Visual Studio Editor does not underline errors anymore

Question

My Visual Studio (2008) Editor has stopped to underline Errors (this nifty wavy red lines). I can\'t really tell when, but it can be related to the installation of .Net Fram

Answer 1

About possible causes.

For VS 2012 and 2013 if you have more than one instance of Visual Studio on different machines binded to one "live" account and have installed ReSharper on one of them, it disables the native IntelliSense and error underlines (to replace by it's own rules) that will be synchronised through your account to another machine without ReSharper.