You have Malware installed which keeps resetting your Firefox pref for the homepage. You need to get rid of that Malware.

HiJackThis should be able to locate and remove that.
http://download.cnet.com/Trend-Micro-HijackThis/3000-8022_4-10227353.html
Or you can attempt to locate the offending files and manually remove them, if you have an idea of which program you installed dumped that Malware on your PC.
http://www.computing.net/answers/security/searchqu-uninstall-how-to/33902.html

See also these threads about searchqu:

• /questions/816181
• /questions/790833

Hello!

My name is John, and I'm a member of the Searchqu Support Team. I'm here to assist :) @Louisela-when the software installed onto your pc it offered two basic installs, typical installation, which lists the add-on features such as searchqu default search, and Custom installation, which allows you to select the add-ons that you wish to install. There's no need to worry if you did the typical install - this isn't a virus,nor malware, and there's no need to Perform a virus scan against it.

Please follow the instructions below in order to change Searchqu as your homepage setting:

1.Go to Control Panel > Add/Remove Programs > look for windows searchqu toolbar > Uninstall

2.Write in the URL address: "about:config" It'll warn you to be careful. Go in anyway. Search for:"homepage". In the filter and double click "browser.startup.homepage" from here you can change your default homepage to a multitude of sites.

If you followed the instructions and still can't find a solution to the issue, please don't hesitate to let us know and we will walk you through it :)

The Searchqu support team