Huh? If everything but one browser works, the suggestion will be to avoid using that browser unless you can show the expensive equip is doing something wrong.
So firefox doing nothing more than a connection reset message does not help at all.
A trouble ticket that says chrome works, wget works, curl works, IE works, but my firefox browser with 10 privacy plugins does not work - is NOT going to get a good response from you support contact.
So, it sounds like FF is sending something that's causing an RST to be emitted from either the website or (more likely) your appliance. Next step would be to pcap/tcpdump a connection from both a working browser and FF, and see what the difference is. That kind of information is a lot more useful to FF devs than "something is happening that causes an RST from someone".
So firefox doing nothing more than a connection reset message does not help at all.
A trouble ticket that says chrome works, wget works, curl works, IE works, but my firefox browser with 10 privacy plugins does not work - is NOT going to get a good response from you support contact.