I have the same issue. Done all the usual like trash prefs, reinstalled, removed 3rdparty plugs... but it's still there. Turning off the network doesn't seem to make any difference. It gets better for 20sec and then the problem is back. Unusable, currently PT is a virtual door stop......
Presumably Ilok is the problem as I updated to 5.2.1 yesterday. Did remove and reinstall but....
Vid here:
https://www.youtube.com/watch?v=vEGZ...ature=youtu.be