Mail crashes after attaching an attachment

Question

Since change to Leopard, Apple Mail crashes when trying to attach an attachment.
Any ideas?
Thank you

Answer 1

A brief update:
Here are the list of my symptoms, and the things I tried.
Adding attachments to Mail.app or Safari crashes the apps. Problem is sporadic, but happens more than 80 percent of the time. Other apps that require a drop down menu crash coming out of the menu (like Grab).
I have no 3rd party add-on apps, and nothing other than the Airport base station agent in my startup items. I'm also experiencing 30 seconds of beach ball upon starting safari. And when I open Mail.app, I've got to go click on a sidebar mailbox for anything to show up in the viewing window.
My machine is a June 2009 13" MacBook Pro. After purchase, I used migration assistant to bring over content from my late 2004 PowerBook G4, a machine that was running Leopard, itself installed as an upgrade Install on top of 10.3.
Fixes tried:
1) Repaired permissions (nothing needed repair)
2) Repaired disk (no problems)
3) Fixed duplicate fonts (did not help)
4) started in safe mode (did not help)
5) PRAM reset (did not help)
6) Trashed preferences (various, but did not help)
7) Rebuilt mailbox (did not help)
8) Actually went in and deleted duplicate fonts (did not help)
9) Validated fonts, deleted the one unusable font (did not help)
10) Couldn't nuke font caches, but rebooted in safe mode again (did not help)
11) Tested under new user -- THIS RESOLVED THE PROBLEM!!! And things in this new user identity are very zippy. Safari runs very fast.
So I isolated it to something specific to my user identity. I then started poking around my user/Library folder. There are remnants of things in there that are from applications I no longer use. I got rid of these, moving them to the trash and then checking to see if the crashing problem persists.
There were some contextual menu items stuff (which don't work on SL) and some .framework stuff that I had no reason to keep around. After trashing these, I have yet to be able to recreate a Mail.app or Safari crash. However, I can create a Grab.app crash, and Safari still starts up with the 30-seconds of beach ball.
I am currently methodically going through and purging other things in my user folder that I don't need. But I may switch to bringing things into the other user identity to drill down on this. I actually like that idea better, since it is a cleaner identity, free of my 5 years of history dating back to the PowerBook G4 days.