One of the thing I hate about firefox is that when you have internal certificates like those issued by HP Integrated Lights-Out’s (iLO) web page, you have to confirm to download the cert and add it to your cert store. There is no one-click solution to this as yet and neither can I disable this in FireFox even if I only intend to use it in an intranet environment.
More troublesome is when I update the firmware in my iLO and hence a new certificate is generated and when you try to launch the web page for iLO access again you will encounter the following error.
Error code: sec_error_reused_issuer_and_serial
It took me a while to figure it out from googling, but the solution is simply to delete the cert8.db from your FireFox profile, usually found in C:\Documents and Settings\<yourname>\Application Data\Mozilla\Firefox\Profiles\<yourprofile>. Easier still just search for cert8.db in your computer and delete that file.
Oh….. you need close FireFox first