Firefox stops responding then won't open after closing

Frequenly Firefox Portable stops connecting to "any" website, it just spins and searches. Then if I close and try to reopen it, I get the message that it is already running and I have to reboot to get it to start working again.

Running from a thumb drive
Haven't renamed from the installation name i.e. still FireFoxPortable.exe
I can close out all processes in the Windows Task Manager except one "firefox.exe"
I am not really using the desktop version of FireFox anymore.
IE still works normally when this occurs.

Thanks for any help