I went thru the same hassle as k0r did last week on my Dual 800... After trying everything, I did the last thing I ever do - I called Apple - and they basically said I was "hosed" and had to re-install EVERYTHING again. Every time I quickly install a new "update" of anything (particularly Apple OS updates) I could kick my self in the butt. This has happened to me in the past and I let myself get suckered again. Take my advice and wait for a 10.2 update...