I use Firefox 40.0.1 on my Windows 7 PC with the start-up page set to my own site www.drivingnt.com
For some time now when firing up Firefox Chrome or Explorer, the browser comes up with an "Omniboxes" logo and search box instead.

I've tried changing it back in Firefox's options but there's no action button to click on after I've typed the necessary info into the "When Firefox starts" and Home Page URL boxes, and after exiting the Options page, nothing has changed.
Chrome and Explorer fire up with the Omniboxes page too but I haven't tried changing the settings on these browsers (I only use them when working with CC HTML Editor).
Running an antivirus scan with Avira antivirus doesn't help.

I'm assuming Omniboxes has taken over Firefox (and the other two browsers) but I don't know how to fix this - can anyone offer any suggestions?

Try Malwarebytes.org and download their free version and scan for spyware and malware.

Zipper, Google 'omniboxes remove' -lots of good advice for all browsers

Hope this helps
Dave

Thanks for the advice!
I used Spyhunter - it wasn't free but it fixed the issue.