Mail crashes after software updates

Question

I'm working in OSX.2.8 and yesterday downloaded some software updates, including security updates. Today, both Mail and Safari won't launch. Mail starts to launch then crashes, and I get that message "the application has unexpectedly quit, the system and other apps have not been affected." Safari doesn't launch at all - the icon on my dock bounces a few times, but nothing else happens.
I have tried dumping the Mail preferences but the problem was not solved. Any advice would be much appreciated!

Answer 1

All your mailboxes appear empty after the
conversion?!
Yes!
Which steps did you follow to upgrade to Tiger? Did
you do an Archive and Install of the new
system or did you do something else?
Er, no, I did not do Archive and Install. I just installed it via FireWire from my husband's computer, because my computer doesn't have a DVD driver. I didn't lose any other files though, just my emails.
Did Mail automatically proceed to import your mail
when launched for the first time after having
upgraded to Tiger, or did you do something in order
for that to happen?
It offered to import my mail, so I said OK.
How many accounts do you have and what type are they
(POP, IMAP, .Mac)? How is your Mail organized? Do you
archive it in "On My Mac" custom mailboxes?
I have three accounts, all POP. If by "On My Mac custom mailboxes" you mean mailboxes that I created, then yes, that's where they were archived. I was kind of expecting to lose my Inbox but not everything else.
JW