I have crappy internet at home (comcast) so I find that after playing a more bandwidth-intensive game like EIR for a period of time (or torrenting overnight) I need to power-cycle my modem+router (aka, unplug them for a few seconds and plug them back in) to get back to optimal effectiveness. I usually end up doing this after every few games in a row.
Of course, this might have nothing to do with your problem. Also, wireless sucks