You should contact Roboform about that problem and file a Bug report with them.

If you would provide a BreakPad crash report number from Firefox, maybe someone here nay see something else wrong that might be fixable from your end.
https://support.mozilla.com/en-US/kb/Firefox%20crashes#w_getting-help-with-your-crash

Type about:crashes in the URL bar and hit Enter.
Click the hyperlinks to bring up the Crash Report pages and copy'n'paste the URL of each of those reports into the message box here. It can take a few minutes to bring up each crash report for the first time, but once they're called up repeat visits are much quicker.

Thank you for the elaborate explanation.

I've written to Roboform as you suggested. I've downgraded to Firefox 4. I'd rather wait for an answer fron them before upgrading again.

Best regards.