Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

• Don't make any changes on the Safe mode start window.

See:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems
• Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

The search icon is still Yahoo in safe mode, but i discovered there is a drop down list of search engines, and that the 7zip download only made yahoo the selected one. I used "manage search engines" tool to revert selection to google, thus the problem is solved