iPhone Dropping Wireless Connection

Hey everyone, every since I moved to a protected wireless network (WPA-2 Personal) my iPhone has been dropping the wireless connection randomly. I have to go back into settings and choose my wireless network again. This wouldn't be so much of a problem, except that I'm using too much data on my 3G and I might get charges for overuse.

I have an iPhone 4 on AT&T, by the way.

Thanks!

Settings > wi-fi > under choose a network tap the blue circled arrow thats your network and under IP address make sure its DHCP then at the bottom tap renew lease.
Also if your wireless router has channel selection on auto select manual and pick one with the least amount of traffic.