Projects solution building

I am trying to build a solution consisting of 45 projects, but there is some problems. I get the (unable to determine name) in the solution explorer.

What causes this? Can it be because some projects have been removed. There were 2 obsolete projects that were deleted. It's kind of indicated in the error output.

Here is the errors generated:

I came to find a solution similar to the posted problem. Hope this helps http://msdn.microsoft.com/en-us/library/xsyw70ef(v=vs.80).aspx