After upgrading to photoshop cs2, I run into a bug where if I am browsing a
folder with ACDSee 3 and then I try to save a new psd file into that folder
with photoshop, I will get an error from photoshop about that file being in
use.

If I navigate ACDSee away from that folder, then I can save the file from
photoshop. Then I can point ACDSee back to that folder.

This is what I think is going on (pure guess):
photoshop create a blank file in the destination folder
ACDSee detects the new blank file and opens it to display
at the same time photoshop tries to open it again to save data but the file
is now locked by ACDSee for reading

Version 6 of photoshop + ACDSee 3 do not have this problem.

Now, who should I file the bug report with?