I have had the same problem with Firefox and also remembering my login information in Vista. The XP operating system is fine the problem is only with Microsoft's Vista operating system. It could have something to do with Vista's security setup, either that or Microsoft is just kicking the competition around? Actually it's probably a little bit of both those reasons.

The only way I have been able to correct the problem is to download the IE Tab add-on. It allows you to set up a tab to open with the IE engine embedded. If you have a site that is giving you login problems, when it is open select the tools button. In the dropdown box select the IE Tab Options. The problem web site should be highlighted in the pop-up display box. Select the add button to the right and it will transfer the web site to the list of sites that you want to open with the IE operating engine.

Now that web site will always open under the IE operating engine when you start up Firefox. After you login to that web site if you go back to the tools button and select options again, you can save all opened tabs as your home page. Now when you start up Firefox you will still have all the advantages of Firefox and those hard to login web sites will automatically load and sign you in the same as they did before.

Someday Microsoft will probably stop teasing Firefox and let them in on what they have to do to get around this obstacle, but then again maybe not.

I dont thinkyou have a problem wit your browser .

but anyways i will get you the link for downloading latest version of vista.
http://download.mozilla.org/?product=firefox-3.0.3&os=win&lang=en-US

but stil if u ve same problem i will give some basic browser trouble shootin steps ,
follow that,

in the menu bar,
press tools>delete private data> put al the ticks den click delete this will delete the temporary files

if this doesn resolve your problem,

try with diffrent browsers like netscape or opera !

these browsers are as good as mozilla