Cannot choose home page in FireFox

I am new to Linux but have run all Windows versions right up from DOS. I have had my AA1 for 2 weeks now and everything was working fine till today. I find FireFox reverts to the Welcome to FireFox/Yahoo Search home page. I have tried several ways to specify Google as my home page but after closing FireFox and re-opening it the same FireFox/Yahoo Search url is home page again. I had no trouble choosing Google url as home page before. Now it just won't stick! Something must have screwed up cause a window pops up in some web sites I go to, warning me that I am sending info over an unencrypted network and can be read by a third party ("warn me each time box" is unchecked so it shoudn't do this). Also when in the FireFox preference box I click on the button that - asks me where to save downloads to - and after closing FireFox and re-opening it defaults to "desktop" as the place where downloads are saved. The only things I have changed are I added KeePass password protect prog. thru add/remove software after enabling XFCE desktop menu, and I changed my WiFi security from WEP to WPA/WPA2 personal. All programs except FireFox seem to be working fine.
Any ideas how I can fix this?

 

Open the help page in FF, and look for 'open profile manager'
create a new profile, don't import details from the old profile, that should fix it.

Keith

 

Thank you Keith!
I will change my profile when I get home from work today and see if that fixes FireFox.
I appreciate your help.

 

I entered a new profile in FireFox and everything works now! Thanks Keith for the help. Much appreciated.