i9300 wireless not working

I have a wireless router with 4 computer on it, 1 is plugged into it, and 2 are usuing wireless connections, all 3 are working fine, but my i9300 is not connecting wirelessly, i can connect it witha cat5 cable, but the wireless connection says that no wireless networks were found within range, does anybody have any ideas, it seemed to lose its connection after i upgraded from 512mb of ram to 1.25Gb of ram if that has anything to do with it, thanks for your help.