I've installed the Gallery module and have setup several pages and albums but am having some trouble.  I setup 3 pages using the gallery module, the first 2 only have 5 - 12 photos each and they seem to work fine, the third page has 5 albums in it and some of the galleries have 270+ photos, that's the one I'm having trouble with.

Some times it loads slow but does load, about 80% of the time I get:

A critical error has occurred.
Object reference not set to an instance of an object.

One time I received a page with the following but the rest of the DNN site didn't come up:

An error has occurred.
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 DotNetNuke.Modules.Gallery.WebControls.Pager.Page_Load(Object sender, EventArgs e) at System.Web.UI.Control.OnLoad(EventArgs e) at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace ---

I populated all the galleries by uploading all the files to their respective _source folders, then ran the Maintenance, checked them all and synchronized them.  Which brings up 2 more problems, the first is that every time I've tried the Check All box I have to do it twice before it actually check marks each photo, the second is that twice I've received the following error while trying to go into the maintenance:

A critical error has occurred.
The process cannot access the file 'D:\WWW\mainefreeze.com\wwwroot\dnn\Portals\0\Gallery\379\Crush 05-27-06\_metadata.resources' because it is being used by another process.

This is the reason why I added seperate pages for the other 2 galleries instead of just adding more albums, if I add the photos in more albums then none of the galleries will come up, this way at least the first 2 sets of photos display.

Any ideas on what I can do to fix these errors?

I figured it was just too many pics but was hoping that there was come tweak I could do to make it work better with large numbers of photos.  I had already optimized and resized all the photos before putting them in the gallery, so that didn't help with the error.  I don't think it loads all 270 on any one page, just 6 per page with many pages, unless it's loading them in the background when you go to the album.  Had to go in and delete the whole page, I couldn't get it to load at all any more. 

First, as a little background on what is happening:

When a web request comes in for the gallery module, the gallery module looks to see if it has a cache already setup in memory for all of the pictures in the albumn.  If it does, it create the page and sends it back to the user.  If it does not have a cache, it goes and checks all of the files, adding them to the cache, and (possibly) updating the _metadata.resources(configuration/settings/data) file.

The problem is that if two requests come in at the same time requesting an albumn while the cache isn't built, both requests will end up trying to recreate the cache.  An example is if the person gets impatient and hits the refresh button in their browser.  Should the settings file need to be updated during those cache rebuilds (which unfortunately it does more often than really necessary) you will get two processes trying to update the file--and thereby the error mentioned.

One solution is what others have mentioned and that is to limit the size of the albumns.  Basically if the albumns are small, the cache can be created quicker.

The other is to be patient during the first load of the cache.  If you change settings in the module, add pictures, upload pictures, etc, the cache needs to be rebuilt and you just need to wait the time (which for me is usually like 20 seconds) and once the cache is built all future requests should work just fine.  While I haven't tested all of the code paths, this error should really only occur when an admin is messing with the site.  Once things are setup and the cache is built, there shouldn't be any errors.

I put together a sample site on my computer with 1,004 pictures in it and if you waited the 30 seconds for the cache to load, the rest of the requests went quickly with no problem.  BTW: I tested it with 500 pictures on a page at a time (5 columns by 100 rows), 2 pages.

Trust and be patient, my son.......