When I launch PortableFilezilla that comes with Portable Apps Suite 1.0 Beta, I see a PortableFilezilla splash screen for a couple of seconds, then nothing. The led on my USB drive stops flickering. There is a FileZilla process that's still running, but I can't kill it. My task manager crashes, in fact, when I try to "End Process" the FileZilla.exe process! I've never seen that happen before, ever. I'm running Windows 2000.
So perhaps this is not a big deal. What probably happened was that my firewall software asked if it was OK for that exe to be started, but this window "popped under".