I've been developing a class library for quite sometime and all of the sudden, sometime last week, I opened my project and all of my references have yellow exclamation points on them now (System.dll, System.Drawing.dll, etc..). I've tried removing the references and re-adding them to fix any broken reference paths, but they continue to show yellow exclamation points on them.
Nothing had changed since the last time I'd opened the project. The only thing that was different from the last time I'd opened the project was that this time I opened it from directly inside of .NET from another project. For example, I was working on a .NET 3.5 web project, then clicked File -> Open Recent Files -> My Other Solution. This closed my current current 3.5 web solution and opened the 2.0 class library solution and the problem appeared for the first time. I'm not sure how (or why) this would cause a problem, but I'm leaning toward the fact that Visual Studio got confused or something and now my assemblies are all invalid on this 2.0 class library project. (?)
What would cause this to happen and how can I fix it? I've looked around the web, but I only see that people have suggested to remove the references and re-add them; which I've done, to no avail.
I'm considering starting a new project and copying over all of my source files one by one, but would really like to avoid all this if possible.
Thanks in advance!