Do things one at a time.
As a thought, can you load this page:
http://www.mousebits.com/index.php?page=upload
The cache you need to clear, not the history etc .
Go to tools-options-privacy.
There are two buttons - clear recent history and clear cookies.
Click on the clear history button . This brings up a drop down with the choices you want to clear - from the last hour to everything.
Select everything (don't worry, it doesn't do anything yet).
CLICK ON THE DETAILS + sign
uncheck everything bar cache
Then click the button with the tick that says "clear now".
It shouldn't clear the pass words as they are not held in the cache but, in case, under the security tab for Firefox options-tools-security , there is a list of your saved passwords and an option to show the passwords. Take a screen shot of the list and save it - just in case.