That sounds suspicious. Some add-on or service might have taken over your normal address bar search.

Is it true (as your browser reported to the forum software) that you are running Firefox 10.0? That version was released on January 31, 2012 and contains numerous publicly disclosed security vulnerabilities. You should update if you can. If Help > About Firefox > Check for Updates says there are no updates available for you, that's a different problem.

Back to your search issue. Try this add-on to reset your search providers to the default. If it changes back, look for a rogue extension.

(1) Search Reset: https://addons.mozilla.org/firefox/addon/searchreset/

(2) Extensions:

orange Firefox button or classic Tools menu > Add-ons > Extensions category

Basically, disable everything non-essential and restart. Take nothing for granted, because malware providers may use names like Mozilla, Firefox, and other software publishers and popular websites in the names of rogue extensions.

Any luck?

The search reset gave me the opertunity to select Google which I did. This solved my problem. Many thanks for your help.