A coworker recently got this error when trying to open a web application project within Visual Studio 2008:
An application has made an attempt to load the C runtime library incorrectly. Please contact the application's support team for more information.
Note that in this case, (1) Visual Studio opened just fine, (2) the problem was in merely loading a web project, and (3) nothing was even being compiled yet.
It turned out the problem was likely from a corrupt uninstall of the .Net 3.5 SP1. By re-installing the SP, things began to work again.
NOTE: .Net 3.5 SP1 has a potential error with the web dlls, so you may need to make some tweaks to the GAC.