As Firefox 5 is no longer supported it is [https://support.mozilla.com/en-US/forums/contributors/707522#post-41913 recommended] you use Firefox 3.6. As you may only use Firefox 3.6 for the one site it may be worth considering Firefox portable, you are then able to use your ordinary Firefox 6 day to day, and keep all your settings and passwords, and just use Firefox 3.6 portable for the one site. What is the bank you use ? <br/> (From your system details I guess you are on 3.6 at present)<br/> When you are on Firefox 6 use the feedback button to report the problem with the Bank Site. (I am not sure that can be done with Firefox 3.6, it could not be done earlier this year) link http://input.mozilla.com/feedback