I was having an issue just like that and I found that turning off my Avast (anti-virus program) for 10 minutes did the trick. After the 10 minutes is up and the program resumes running as if I still had the program on pause, though it will automatically kick Windows Firewall up, that shouldn't be an issue. I do this every time I go into any of the rooms on WM, haven't tried it elsewhere, since I am not allowed anywhere else, and I don't play in other realms off this site, so I don't know if it will fix the lag problem on other sites, though I would think it would.
Am not sure if there is a conflict between the anti-virus programs, as I am thinking the solution to the problem will be solved using other anti-virus programs, but I was at my wits end, having to post to all in the room that I was having huge lag issues, and I would have to PM to myself posts, just to get a post that was just sent to me by someone else, or to get the number to my dice roll for an event tossed at me by ST during our migration. I would suggest, that if that fails to work, I am sure someone else will come along with a suggestion or possibly a solution.