Multiple Users at Once?

Hello,

I'm trying to use Firefox portable for a backwards reason that it was probably designed. I want to put it on a network drive and allow multiple people to access it at the same time. The first person can launch the program with no problems. Each person thereafter will get this error:

"Firefox is already running, but is not responding. To open a new window, you much first close the existing Firefox process, or restart your system".

Any thoughts?

-Ian