Thunderbird not starting

Since yesterday I get the following error when starting ThunderbirdPortable:
http://test2.slibbe.org/XUL%20Runner.png

This is on various Windows 7 laptops, and current Pre-Release 2.1 PortableApps Platform, either running form hard drive or USB microSD card.

Anybody else having the same problem and any ideas how to fix this?

Greets,

slibbe