Cannot open 1.5.0.9

Thunderbird Portable 1.5.0.5 works great for me. I downloaded and installed Thunderbird Portable 1.5.0.9 on my local hard drive.

When I double click ThunderbirdPortable.exe nothing happens. If I watch the task manager, I see ThunderbirdPortable for about a second and then it quits. The splash screen never appears and there are no errors.

I tried renaming renaming Thunderbird.exe and added a .ini file pointing to it, but got the same result. I know the .ini file is working because if I give a bad name for the exe I get an error.

I have this same behavior with Firefox Portable 2.0 but FileZilla Portable 2.2.30a works fine.

Any ideas?

Thanks,
Steve