This is just a stab in the dark, but I think I may have experienced this before, and it usually happens after a rude disconnection. In my case, upon reconnecting, my bandwidth was somehow reduced to a lower number than the one I subscribed to. A simple manual disconnect/reconnect solved it for me. Or it could be you were unlucky and got a badly routed IP upon reconnecting. In both cases, the solution is the same.
If after several attempts at obtaining a new IP fails to restore your original speed, you might want to do a speedtest to see if TM accidentally miscapped your line.
Hope it works out for you. Do keep us updated.