iTunes has a "feature" where podcasts that haven't been listened to in some amount of time are no longer updated automatically. To fix this, I simply run an AppleScript daily from iCal (I could use cron to do this instead) that increments the play count of Podcasts that haven't been played (granted, this ruins the accuracy of the play count, if you actually care).
tell application "iTunes"
set pl to (some playlist whose special kind is Podcasts)
set ofi to fixed indexing
set fixed indexing to true
repeat with t from 1 to (count of file tracks of pl)
set tr to file track t of pl
try
if tr's played count is 0 then
set tr's played count to 1
end if
end try
end repeat
set fixed indexing to ofi
end tell
Just save this to a file, create an iCal event that repeats daily, and in the event's Alarm field, choose Run Script and select the script file you just created.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070211132245620