The PS3's wireless capability can be a bit on the dodgy side for some- I've seen quite a few saying they can't get connected/ have a weak signal with the router maybe just 10 feet away from the router.
The problem may lie in the router you are using- their N router may be having problems with backward compatibility to wireless G/B connectivity. They never did finalize specs for 802.11 N routers so most are going by various drafts of specs. I would suggest sticking to the wired connection for now and, if possible, take that router back for refund/ exchange for an 802.11G.