Configuration:
Just my two cents,
I have experienced this issue twice now and it turns out after all of the suggestions I tried, it was BitDefender on my local machine that was doing this. So my fix for this problem is to try adding in exceptions to the local security software into the firewall and AV parts of it. Tell it to ignore the msvsmon.exe and devenv.exe altogether and see what difference that makes.
Otherwise try ripping it off altogether and see if the it lets you debug your solution.
You can see here for more info: http://forum.bitdefender.com/index.php?showtopic=37028
I installed the latest BitDefender version and all was fine for me.