problem migrating Outlook to Thunderbird to Apple Mail

Recent PC->Mac convert, and I am having problems importing my Outlook 2003 mail into Apple Mail 3.2. Here is the process I followed after reading many other threads:

Install Thunderbird on PC and Import Outlook mail
Copy PC Thunderbird profile to external HD
Install Thunderbird on iMac
Create a new profile on Mac Thunderbird and make note of the profile location
Copy PC Thunderbird profile onto the Mac Thunderbird profile location
Open Thunderbird - Verify that all mail made the transition (and it did)
Close Thunderbird, open Apple Mail and import mailbox from Thunderbird
Check all email folders and import!

All looked like it was working well, but when I look at the imported folders in Mail, some email imported and others didn't. It looks like all folders imported but some are empty and some have emails. Any ideas what I did wrong? As I said before, according to some other threads I have read, this method should work.

My system: 24" 3.06gHz iMac w/ Leopard 10.5.2