Firefox portable doesn't work

I keep getting the following error with Firefox Portable:

The application had problem and crashed.

Unfortunately the crash reporter is unable to submit a report for this crash.

Details: The application did not identify itself.

I don't claim the bad grammar; that is how the error was written. My regular firefox works fine. I was able to use the portable version previously. I deleted it and downloaded it again, but it only worked one time. I keep getting this same error every time. Please tell me what I need to do to get this to work right. Thanks!