FirefoxPortable will not start...

...at all. Neither will ThunderbirdPortable.

The splash screen appears. Then nothing. The app vanishes from the process list. Ditto for 7Zip. Notepad++ did throw an exception on the first try, but will start now.

FileZilla, Eraser and SumatraPDF work fine.

I'm using A SanDisk Cruzer micro 4GB USB stick.

Can this be a performance issue? At home I have an old 1,3GHz Celeron system with 768MB RAM with XP Professional (with USB 2, though). At the office computer the apps worked.

r. Ville