Setup:

Vista 32bit Home Premium
QuickBooks Pro 2009
Upgraded to Vista SP1, then SP2

Problem:

When loading up company file in QuickBooks, post SP1/2 installation, we get error 6123.

I found a solution here: http://community.intuit.com/post/detail/a37tRAeBir3zw9abTJhmjm

I needed goto the folder options and un hide hidden folders. Then under c:\users\username\app data\intuit - I was able to find the dbstart.log file referenced buried in some folder. Renamed as suggested, restart the QB services/db and then everything works again.

Wonder how many other things got broken with Vista SP1/SP2 (not to mention, how many hours does it really need to take to install a service pack!!!)? Bring on Windows 7...