(I'm old greg) Corporal

I seem to be suffering from extreme lag when entering the Steamgamers Prisonbreak server. When I enter the game freezes and the "Connection problem" message will appear in the top right hand corner. After a while gameplay resumes, however the lag continues to spike every couple of seconds. My ping is fine and I never used to experience this before. Console doesn't display any sort of error message so I have no idea what's wrong. Could anyone hazard a guess?