[final kaoss]

Well I'm not sure what all you did but... over the past 18 month's I've went from;

example.com/forum
to
example.com/
to
newdomain.com/forum

And wound up with the majority of attachments still working. But yeah aside from the mass search & replace that I mentioned, you shouldn't have touched any other settings, as that mass edit would've changed them all to where they needed to be. So my guess is that you chose to put files in the database instead of storing them locally as files.