Opened up my dotnetnuke environment today and I get a message that states "An unhandled error has occurred." and gives a command button to "return to site".

I cannot access the site to do look at what was done last.  When I go to the exception log in the database it gives me the message below.  On the address bar it states " http://www.domainname.com/Default.aspx?tabid=39&error=Object+reference+not+set+to+an+instance+of+an+object.&content=0 "

Can anyone point me in a direction on what I can modify to at least get into the application again?  I think this happened after installing a module.  Is there a "Safe Mode" that I can start up in that keeps the last item from causing the issue so I can get in and fix it?

<LogProperties><LogProperty><PropertyName>AssemblyVersion</PropertyName><PropertyValue>5..4</PropertyValue></LogProperty><LogProperty><PropertyName>PortalID</PropertyName><PropertyValue>0</PropertyValue></LogProperty><LogProperty><PropertyName>PortalName</PropertyName><PropertyValue>Elise McVeigh's Life Camps</PropertyValue></LogProperty><LogProperty><PropertyName>UserID</PropertyName><PropertyValue>-1</PropertyValue></LogProperty><LogProperty><PropertyName>UserName</PropertyName><PropertyValue /></LogProperty><LogProperty><PropertyName>ActiveTabID</PropertyName><PropertyValue>39</PropertyValue></LogProperty><LogProperty><PropertyName>ActiveTabName</PropertyName><PropertyValue>Home</PropertyValue></LogProperty><LogProperty><PropertyName>RawURL</PropertyName><PropertyValue>/Default.aspx?tabid=39&amp;error=Object+reference+not+set+to+an+instance+of+an+object.&amp;content=0</PropertyValue></LogProperty><LogProperty><PropertyName>AbsoluteURL</PropertyName><PropertyValue>/Default.aspx</PropertyValue></LogProperty><LogProperty><PropertyName>AbsoluteURLReferrer</PropertyName><PropertyValue /></LogProperty><LogProperty><PropertyName>UserAgent</PropertyName><PropertyValue>Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; GTB6.3; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.04506.648; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)</PropertyValue></LogProperty><LogProperty><PropertyName>DefaultDataProvider</PropertyName><PropertyValue>DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider</PropertyValue></LogProperty><LogProperty><PropertyName>ExceptionGUID</PropertyName><PropertyValue>25c96b8d-97d9-4929-bec3-99d8916a174e</PropertyValue></LogProperty><LogProperty><PropertyName>InnerException</PropertyName><PropertyValue>Object reference not set to an instance of an object.</PropertyValue></LogProperty><LogProperty><PropertyName>FileName</PropertyName><PropertyValue /></LogProperty><LogProperty><PropertyName>FileLineNumber</PropertyName><PropertyValue>0</PropertyValue></LogProperty><LogProperty><PropertyName>FileColumnNumber</PropertyName><PropertyValue>0</PropertyValue></LogProperty><LogProperty><PropertyName>Method</PropertyName><PropertyValue>DotNetNuke.UI.Skins.Skin.GetSkin</PropertyValue></LogProperty><LogProperty><PropertyName>StackTrace</PropertyName><PropertyValue /></LogProperty><LogProperty><PropertyName>Message</PropertyName><PropertyValue>DotNetNuke.Services.Exceptions.PageLoadException: Object reference not set to an instance of an object. ---&gt; System.NullReferenceException: Object reference not set to an instance of an object.

at DotNetNuke.UI.Skins.Skin.GetSkin(PageBase Page)

at DotNetNuke.Framework.DefaultPage.Page_Init(Object sender, EventArgs e)

at System.Web.UI.Control.OnInit(EventArgs e)

at System.Web.UI.Page.OnInit(EventArgs e)

at DotNetNuke.Framework.PageBase.OnInit(EventArgs e)

at System.Web.UI.Control.InitRecursive(Control namingContainer)

at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

--- End of inner exception stack trace ---</PropertyValue></LogProperty><LogProperty><PropertyName>Source</PropertyName><PropertyValue /></LogProperty></LogProperties>

To be honest, not sure.  I thought it was an istallation of a module...but after heading down that road in trouble shooting I found out that I have 3 different 5.x.x environments on the same server and they are all now giving me this same error.  Happened sometime on the 8th of December.  Seems to be more environment as I added a brand new instance of the latest code base and it immediately does the same thing immediately after installation.

Is there any way to decipher the stack trace or error being placed in the event log?  Is there any debug mode that I can turn on that would give me more information to go by?

Does notnetnuke 5.x.x automatically update itself? 

Any and all help is greatly appreciated?  If someone knows how to fix this 100% I would be happy to pay for support.

Thank you.

I have been having this problem off and on for 6 months now.  In hind sight and with a lot of installations behind me and as a true advocate for dotnetnuke, I can truly say that if it is a dotnetnuke issue it has always given me more direction and error messaging.  That is what was so hard tracking this one down, for me it was two parts: a security issue and then an intermittent environment issue.

My first solution to errors that were better captured and/or gave the same instance of the error...like files were missing…( object reference not set to an instance of an object )…was the new security of the newer operating systems. "NTFS Streams" (a lot of info on google) which "Block" files from your system unless you agree for them to be used.  Clicking on the downloaded zip files and choosing Properties then UnBlock, opened dotnetnuke system files that would not work without taking of that security restriction.  I did find one command line tool that you could run recursively on files that would delete all of the streams on any directory structure.  This was half of the solution and this problem would give errors that were better described in dotnetnuke and the exact same error.

For the second part of my solution I did search the site and found a post under " An unhandled error has occurred" that pointed to this thread  http://www.dotnetnuke.com/Community/Forums/tabid/795/forumid/107/threadid/146923/scope/posts/Default.aspx , which happened to be my answer. 

The control panel system that I use was creating sites with an Admin folder set up as a virtual directory.  My install would put the right files into this folder so on occasion, usually right after install and for a few days/weeks the site would work, then one day it would go to the "An unhandled error has occurred - return to site" error.  In Internet Information Services Manager it would show the symbol showing a virtual directory on the "Admin" folder.  I simply deleted the virtual directory symbol which on my machine did not delete the admin folder or files and all instances of sites that had the intermittent problem started working again. That was 4 out of 4 newer sites which were all exhibiting this error.  Older instances of dotnetnuke on my servers which have been working were verified not to be the Virtual folder in IIS Manger and all have been flawless in their operation and pleasing their owners.

Again, thank you to all that helped.