Post the top third of the dxdiag report, your in game settings, and a screenie of "ping plotter" to the game servers.
Like you said a bad connection due to the weather will cause the disco's, but the game will drop to the desk top if it doesn't receive data packets as well, which can be due to a crappy connection.
The ping plotter will show how bad your connection might be, the dxdiag will show if your computer really CAN handle the setting your using, and all three together will help get you suggestions to help you out.