An odd things happens to my S every now and again, Normally at home it sits on 4 Bars out of the five straight bars fine that at random moments it lose all signal and a little X shows before the bars and says no service the only way to restore service is to restart, I checked with O2 UK and they say its not a problem with the network. I also updated the firmware as well . Has anyone else experienced this drop out?
If you don't manage to find a fix, I believe there is a solution if S-OFF and rooted on XDA forums that involves flashing a wifi fix zip file. I won't link you, but if you need it, I can pm you the link.