Your Search.us links don't work for me.

To remove the Search.us malware, if you haven't tried this already, you should work through this - http://malwaretips.com/blogs/search-us-com-virus/

Google Search.us for extra information.

The crash report flagged these programs;

dwmapi.dll = Microsoft

ntdll.dll = Microsoft

Nvwgf2um.dll = NVIDIA Compatible D3D10 Driver = NVIDIA Corporation

+++++++++++++++++++++++++++++++++++++

Total Virtual Memory 2147352576

Available Virtual Memory 221523968

System Memory Use Percentage 77

Available Page File 3329687552

Available Physical Memory 726405120

Perform a System File Check to fix corrupted system files Win 7, 8, Vista: https://support.microsoft.com/en-us/kb/929833

See if there are updates for your graphics drivers https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

Thanks to you both for your help.

System File Check came up clear, and checked my graphics driver and that's up to date.

Next step is to follow all the steps at the link alan_r shared to remove the Search Us problem, then I'll know where I stand.

Thanks again.

Try to create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Do a clean reinstall and delete the Firefox program folder before (re)installing a fresh copy of the current Firefox release.

• Download the Firefox installer and save the file to the desktop
  https://www.mozilla.org/en-US/firefox/all/

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

• Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
• (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

Thanks all, just wanted to update.

I followed all of the steps alan_r shared in his comment and have removed Search. us totally from my pc - very pleased!

I also found a couple of plugins out of date I'd missed, so have updated them.

Sadly it is not better at all. Next step is to follow cor-el's advice and test a new profile. I'm also going to do a memcheck, and test my profile on a different laptop, to see if it's a hardware issue.

Will update soon.

Really appreciate your help!