It started yesterday. I turned the PC on, I open Firefox and all the tabs that open the first time you use it were there ( ihave Firefox 3 since launch day). My initial page is the fast dial but it won´t open unless I choose it on the toolbar. All my options change were gone (home page, where I want to download stuff, etc.), but my add-ons remained, my bookmarks too.

Now here comes the big problem. I said, ok I ´ll just use options and put it back the way it was. I change everything, press OK to save it. I close Firefox. I reopen it and it´s back with those "welcome pages" and all the options back to default.

Why won´t my changes in options save? Am I doing something wrong? Can someone that know about this things (cause I know nothing) please help me? Thanks in advance.

solve all the problems:
uninstall, download it agian then install

Yes, there's probably one solution for it, but it would be easier if you just uninstall/reinstall

Problem? With Firefox? Really?

Do you have an antivirus/antispyware/etc. program that is deleting these settings periodically? Try disabling any of that you have and seeing if the problem still occurs.

Thanks everybody for the replies.

@soleron - No. I have an antivirus program and this never happened before. I think I´ll do what blackstar and zexen said.

Thanks again.