Play store not working?? please help!?

[Aspen]

So i have a samsung infuse 4g and when i go to the play store for android it wont let me download apps, idk why. When i click accept & download it says "error retrieving information from server" . Also, when i try to search for apps like instagram or common apps like angry birds, twitter, aviary etc. It doesnt give me any of the apps.. And when i try to search the web for ex. Instagram it says its not compatible with my device..when my device is very much so compatible. My brother has the same phone and it doesnt gice him any trouble.. Please help!!
P.s. I am on a prepaid for at&t ..
It shouldnt matter tho.
Thanks!!

[Joe]

go into settings then manage apps. find play store and google services framework. clear data and cache on both of them. then power off your phone. you can take the battery out for 5-10 seconds or reboot manually into recovery and wipe cache and dalvik cache only. DO NOT WIPE DATA. that should fix it hopefully