wireless internet unusable after 15-30 min.

Hello,

Recently I observed that the wireless Internet connection fails to work after 15 to 30 minutes of usage. If I have skype or GMail notifier on it's even less. Generally what happens is after that 15-30 min, it begins to check for a connection again and then fails to connect. At that point you try to reconnect, but then it's stuck infinitely checking. At this point one of two things happen, it either will freeze the computer to the extent that the power button wont even work (have to force shutdown) or you disable and renable the network which makes the wireless connections not show up as if you only had wired connection.