I ran into a strange bug with firefox locking up each time I pushed a form submit button. When I ran it from the console I had an endless stream of:

    mork warning: unexpected byte in ReadContent()
    mork warning: unexpected byte in ReadContent()
    mork warning: unexpected byte in ReadContent()
    mork warning: unexpected byte in ReadContent()
    mork warning: unexpected byte in ReadContent()
    mork warning: unexpected byte in ReadContent()
    mork warning: unexpected byte in ReadContent()
    mork warning: unexpected byte in ReadContent()

Googling for it revealed an intresting thread which dates this bug to firefox 1.0. Grr.

Here is the fix:

rm -f .mozilla/firefox/*.default/formhistory.dat