theres a list of beep codes for various BIOS's by the way...I keep it in my favs so it's handy to have.
even if he did get the liquid on the mobo, that crap dries up almost instantly so I don't see how that'd be a problem...the vaccuum bristles do cause issues though.
I remember one kid saying he thought that canned air was bad because it forced dust in smaller tighter spaces...personally I never believed that, but it's strange your computer would act up after cleaning it.
BTW, blowing out your PSU is perfectly fine, I do it to mine all the time.
Have you tried resetting the CMOS like Uzi suggested yet? Have you tried turning the PSU off, unpluging it, then putting it back in and turning it on?
It's weird though because like he said, the closest code is video error or RAM
Have you already tried reseating those components?