Then bring it back... it's still within the first your warranty... they will at least give you a refurbished one.
Well, asssuming it's not an issue that is just assocated with the ROM he's running...
It could be one of 3 things:
1. hardware defect
2. radio defect
3. ROM defect
I can confirm that WIFI does work* on my device with BAMF 4.9, but you may have had something go wrong with the install.
*Of course, on every GB ROM I've ever run, my device always shuts WIFI (and ALL data) off when the screen goes into standby when I use WIFI, so I usually do not. Never had this issue with any FROYO roms.