Unity not responding after opening script.

I am using Unity 5.3.2f1 and 5.3.2p3 and with both versions I jave the problem that opening a script takes incredibly long (1 or 2 minutes, sometimes even more) and Unity freezes during the process. I have already tried reimporting all assets but without suceess. It is coming to the point where I am unable to work because I'm just waiting for Unity to finally load Visual Studio any time I get an error or want to open a file. Any thought what might cause it? Thanks!