[Update Oct 31, 2013]: A user pointed out—and I was able to confirm—that SP1 for Windows Server 2008 R2 fixes this issue, so you don’t need the hotfix if you apply SP1. I don’t know whether service packs for other OS’s include the fix.
Gallery Server Pro uses Web.API for many kinds of AJAX callbacks when users interact with the gallery. For example, when you click the area around a thumbnail image, the gallery makes an AJAX call to the server to retrieve the meta items by issuing a GET request similar to this:
As you can see, the URL doesn’t contain a file extension. That is how Web.API is designed and it’s nice and clean. However, a bug in IIS 7 and IIS 7.5 causes extensionless URLs to fail in certain circumstances.
See if you are affected
There are a few ways to identify if you are affected by this bug. The easiest is to navigate to one of the albums in your browser and click the border area immediately around one of the thumbnail images. A wait icon appears in the right column, but it never disappears and the right pane is never updated. If you see this behavior and the web server is running IIS 7.0 or 7.5, you are likely being affected by the bug.
Another easy way to identify the bug is to try synchronizing the gallery (choose Synchronize from the Actions menu). You’ll see the message “Error starting task – An error occurred on the server. Check the gallery’s event log for details.”
When you check the event log, you see this error:
Error: Object reference not set to an instance of an object.
Timestamp: 10/21/2013 4:13:39 PM
Exception Type: System.NullReferenceException
Message: Object reference not set to an instance of an object.
Target Site: Boolean get_IsAuthenticated()
at GalleryServerPro.Web.Api.TaskController.StartSync(SyncOptions syncOptions)
App Event ID: 13
Gallery ID: 1
HTTP User Agent:
Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/30.0.1599.101 Safari/537.36
Apply the fix
A hotfix is available from Microsoft that fixes the issue. It installs quickly but be aware it may require a restart. Once the fix is applied, the Web.API calls work and your gallery is back in business.