Today after pulling latest from our TFS server, and doing a few auto merges (turns out that the AutoMerge is at fault here again)(some day I will learn NOT to trust TFS to do anything, but doubt it) I tried to fire up our Silverlight Browser app and I was presented with this lovely error.

I was a bit stumped by this and did some google searches and everything wanted me to check my IIS settings.  I was pretty sure this could not be the cause because this was all local dev and we have not made any changes.  After digging around in my change log I noticed that during a merge our .xap file was renamed (this was with intent).  However, the server project did not pick up this rename change (technically there were 2 .xap entries in my proj file which did not help either).  So when server was trying to serve up the newly named .xap file it was not found, hence the error

There are 2 possible solutions to this problem (assuming it is non-IIS)

1. Make sure that the .xap file being served up by your server components is in fact the CORRECT .xap file your client wants.  I actually had to open the .proj file directly for the server to make the changes as the IDE will only show one .xap file I wanted.
2. Make sure that your Default.aspx (or what ever page servers ur silverlight .xap file) has the correct file name in the source folder

Hope this helps,

Till next time,