I just installed Mac OS X 10.4 Tiger on my desktop.
After the install, I logged in and the Finder went into an endless cycle of crashing :(
Eventually (as I was attempting to disable various things to narrow down the cause) I got an error from ATSServer complaining about a corrupt font.
Of course, the message made it seem like things would be 'ok' after a logout-login (which they weren't).
I eventually determined that I must just have a corrupt font cache (which I've never had problems with on Mac OS X before, but I've seen reports on the web about other people having problems).
A quick rm /Library/Caches/com.apple.ATS/501/* followed by logout-login seems to have fixed things.
I laugh whenever I have a problem with ATS since an ATS engineer once pointedly ignored me for an extended period of time when I visited UofM to talk to the Apple recruiters (everyone else there was very nice).
Update: It figures that I would start having problems again after a few hours. Finder kept repeatedly crashing (this time more rapidly than before) and other apps were having intermittent problems (having Finder stuck in a crash cycle and also having Terminal crash is 'fun').
I ended up doing an archive and install and things seem to be 'ok' now.
I would rather have known what was causing the problem, but it was easy enough to just fix things that way (and I need to get 'real' work done too).
I've been having the same problem, which I first noticed because InDesign CS stopped recognizing fonts (and would show missing fonts even when I placed them directly into Library/Fonts).
I have FontAgent Pro 3.0.2 installed and initially assumed it was the culprit (do you have it running?) but then noticed the Corrupt fonts warning messages spit out by ATSServer.
Do you have additional info on this problem and how to fix it?
I'm not running FontAgent Pro.
Removing the font cache(s) fixed my problem for a few minutes, but the problems resurfaced.
I ended up doing an 'archive and install' of Mac OS X 10.4 and that fixed it for me.