Vista problem

Thunderbird Portable is running well on Windows XP. I get back with POP protocol my gmail messages on my USB stick. Everything is ok when I want to read offline my emails on XP.

When I want to read them on Vista, I got this message after launching TBportable.exe :
" Could not initialize the browser's security component. The most likely cause is problems with files in your browser's profile directory. Please check that this directory has no read/write restrictions and your hard disk is not full or close to full. It is recommended that you exit the browser and fix the problem. If you continue to use this browser session, you might see incorrect browser behavior when accessing security features."
TB is starting after this message but there are no email.

What's wrong ?