We've just pushed out a small update which offers improved detection of lost connections, particularly in the situation where you've left your computer for a long period of time, then come back to use Roll20 (e.g. your computer went to sleep, you have a laptop and you closed it, didn't use it for 6 hours, then opened it back up and started using Roll20 again).  Basically, please let me know if you start getting the red connection error message when you actually should have a connection :-). Thanks!