Mail.app crashes on opening - no plist file to delete

Question

This started happening a couple of days ago. Every time I open the mail app, it freezes (spinning beachball) and then crashes. Attached below is the most recent crash report. I apparently don't have the plist file that everyone says to delete.
So what are my options? I've looked at other threads, and they're not quite helpful for me.
Chapps
Truncated version of the crash log (not sure you want the whole thing, since it's huge):
Process: Mail [442]
Path: /Applications/Mail.app/Contents/MacOS/Mail
Identifier: com.apple.mail
Version: 4.2 (1077)
Build Info: Mail-10770000~4
Code Type: X86-64 (Native)
Parent Process: launchd [115]
Date/Time: 2010-02-17 20:32:38.247 -0800
OS Version: Mac OS X 10.6.2 (10C540)
Report Version: 6
Interval Since Last Report: 1540351 sec
Crashes Since Last Report: 11
Per-App Interval Since Last Report: 418964 sec
Per-App Crashes Since Last Report: 9
Anonymous UUID: 8884D48A-EFA0-4945-8670-DABE56730CE4
Exception Type: EXCBADACCESS (SIGBUS)
Exception Codes: KERNPROTECTIONFAILURE at 0x000000010fc83fb8
Crashed Thread: 13 Dispatch queue: com.apple.root.default-priority
Application Specific Information:
-[POPAccount saveCache]
-[MailApp _tellSyncServicesToRegisterAndSync]
-[POPAccount fetchSynchronouslyIsAuto:]
-[MessageRouter routeQueuedMessages]

Answer 1

Ugh. Well, got far enough to import my old mailboxes and set up my accounts when the app crashed. I got rid of the plist file once again, Mail started up with no problem ... then crashed.
Here's the most recent crash log header:
Process: Mail [818]
Path: /Applications/Mail.app/Contents/MacOS/Mail
Identifier: com.apple.mail
Version: 4.2 (1077)
Build Info: Mail-10770000~4
Code Type: X86-64 (Native)
Parent Process: launchd [115]
Date/Time: 2010-02-17 21:32:40.620 -0800
OS Version: Mac OS X 10.6.2 (10C540)
Report Version: 6
Interval Since Last Report: 1543874 sec
Crashes Since Last Report: 15
Per-App Interval Since Last Report: 421070 sec
Per-App Crashes Since Last Report: 12
Anonymous UUID: 8884D48A-EFA0-4945-8670-DABE56730CE4
Exception Type: EXCBADINSTRUCTION (SIGILL)
Exception Codes: 0x0000000000000001, 0x0000000000000000
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Application Specific Information:
-[AccountSetupValidator _validate]
objc[818]: alt handlers in objc runtime are buggy!