If you have AVG Safe Search Extension enabled, disable it, and try again.

otherwise

in Options window then Advanced panel then General tab then Browsing session, UNCHECK Use hardware acceleration when available, click OK to save it, exit firefox and restart it.

see for more info : Options window - Advanced panel

thank you

Please mark "Solved" the answer that really solve the problem, to help others with a similar problem.

Thanks, and darn. This is the first update in quite a while that did not disable AVG Safe Search automatically because of incompatibility. I thought perhaps the conflict had been resolved. Guess not. At least "Enter" works on the URL line again.

See:

• http://www.mozilla.org/en-US/firefox/10.0/releasenotes/

Most add-ons are now compatible with new versions of Firefox by default

Actually, I only had one add-on that was not compatible with the last several updates. I have three incompatible with this one. (Two of which were identified during installation, and one of which disabled the "enter" key in the URL line, but which was not identified during installation as incompatible.)