Wow, that’s a pretty non-descriptive error message, isn’t it? And the funny thing is, that particular item number is always the same! What the heck is this?
This is an error message you can get in Visual Studio. I don't know if this is specific to SSRS report projects or not, but I suspect it is. I ran into the error when trying to open a solution with a .rptproj.
Googling finds all sorts of stuff about deleting a line out of the rptproj file and rebinding to source control (most mention Source Safe, but I use TFS and still had the issue). Also, this was in VS2005 (because we're using SSRS 2005 … and the reason for that is a story for another day).
It turns out, this guy had the answer all along and it didn't involve mucking about with the .rptproj file!
The issue is caused because someone checked in their .rptproj.user file. That's the only thing wrong! The .user file is specific to a particular user and should never be checked in (I don't know why it was to begin with). The solution is easy ... check out the .user file and then delete it. I couldn't delete it from TFS (because other people had done the same thing and you can't delete a file from TFS if it has pending changes). But, you can just delete it from your own folder, then re-open your solution and all will be fixed!