Getting the following error, not sure if its skin related or what is the cause.  Only happens sporadically.  Site will work fine for a while then every so often on a page load this error happens, then refresh and it is fine.  Could it be the skin or is it a core bug?

AssemblyVersion: 04.03.04
PortalID: 0
PortalName: Queen Street Studios
UserID: -1
UserName:
ActiveTabID: 54
ActiveTabName: Contact QSS
RawURL: /ContactQSS/tabid/54/Default.aspx
AbsoluteURL: /Default.aspx
AbsoluteURLReferrer:
UserAgent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: 69a826c2-3286-4a4a-a89b-1485e65a6db1
InnerException: Object reference not set to an instance of an object.
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: Solpart.WebControls.SolpartMenu.BrowserSupportsFunctionality
StackTrace:
Message: DotNetNuke.Services.Exceptions.PageLoadException: Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object. at Solpart.WebControls.SolpartMenu.BrowserSupportsFunctionality(ClientFunctionalityEnums eFunctionality) at Solpart.WebControls.SolpartMenu.DownLevelBrowser() at Solpart.WebControls.SolpartMenu.getBorderStyle(String type, String color, Int32 width) at Solpart.WebControls.SolpartMenu.WriteCSSStyles() at Solpart.WebControls.SolpartMenu.Page_PreRender(Object sender, EventArgs e) at System.EventHandler.Invoke(Object sender, EventArgs e) at System.Web.UI.Control.OnPreRender(EventArgs e) at DotNetNuke.Framework.PageBase.OnPreRender(EventArgs evt) at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace ---
Source:
Server Name: JILLC-WIN16

I have this same problme.  This problem appeared for me when I upgraded to dnn 4.0.3.  I was hoping that the upgrade to 4.3.4 would solve the problem but it did not.  What is odd is that I have never been able to re-create the problem when I access the site, it only happens for my users on a seemingly random basis.  If anybody has an idea on how to fix this, I am willing to try it out.

Most likely the lack of a core team response to this issue is it appears to be generated by Solpart (3rd party menu).  Seeing, that I am the author of the menu, I probably would be the only one able to answer the question.  I have been involved in many other things and have not modified the menu since June of 2005.   The fact that these errors just started to come up now is interesting to me... 

Has anyone been able to reliably reproduce this behavior?

My initial guess has to do with the way the menu caches the spmenucaps.config file, since the problem appears to be related to .NET 2.x.  We had issues with this in the core and Solpart may suffer from the same type of code.  Has anyone been getting this error on the .NET 1.x framework?

I will try an schedule some time to research this week.  Any feedback regarding this will be helpful.  Feel free to email me directly if you have any additional insight.