MacCast listener Clark sent this warning for PGP users who are considering moving to Tiger:
A note for those using PGP 8.x and Tiger. This combination also
causes problems, especially with Mail.
Symptoms are things like loosing your mailboxes and loosing your POP
entries. Literally you enter the POP information. After attempting
you will receive a message indicating that new attributes are
available for synch. You are asked if you would you like to save
them. If you select yes,
your POP entries and usually your mailboxes are toast! They are
still available in Library/Mail, but now you really need to be a geek
to rebuild your entries.
Solution: Dump PGP for now. Stability will return and life will once
again be like having a crisp Granny Smith’s on a warm summer day!
There is a note on the problem at http://www.pgp.com/products/tiger.html
So if you are using PGP, quit for awhile.
I do not know if this affects the GNU version of PGP (PGPFree) yet.