hello hazey_sunshine, sorry for the inconvenience but the crash id you've provided indicates that the issue is malware related. the malicious file on your pc causing the crash is named astktkra.dll (randomly generated filename).

according to reports from other users this threat should be detected & removed by microsoft safety scanner, so please do a full scan with this product: http://www.microsoft.com/security/scanner/default.aspx

Well, I have now run that scanner which took two hours, after scanning all the drives with various other trusted software and it still crashes. I ran the scanner, it found two errors, fixed them, I rebooted just to make sure... and no, still crashing on start up just the same. The first time I pressed 'restart' on the crash report box it allowed me the option to start in safe mode or reset - safe mode wouldn't open, and the reset was completed but made no difference.

It also doesn't answer why it keeps auto-updating. If it stopped doing that I wouldn't be having a problem. I would happily carry on using v17 which actually works. 

So, any other suggestions anyone?

did the scan pick up the file, i've mentioned in my prior post?

another user also reported that it was possible to take it out manually out of the windows auto-run programs by pressing windows-key + R & opening msconfig - this reportedly stopped the crashes in firefox too. however you should obviously still try to get the malware totally deleted from your computer. here's more technical information on it: www.microsoft.com/security/portal/threat/encyclopedia/entry.aspx?Name=Trojan%3AWin32%2FTracur.AU

Troubleshoot Firefox issues caused by malware

This crash is usually caused by to malware and the involved randomly named file in your case is astktkra.dll as you can see in the modules list of the crash report.

Try to use MSConfig and disable that file to prevent it from getting started.

• http://www.howtogeek.com/74523/how-to-disable-startup-programs-in-windows/

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) to see if that allows to locate and remove the file either manually or with a malware scanner.

You will have to search the Windows registry (Ctrl+F) for references to that file and export and remove involved keys to avoid startup issues with missing files or alternatively use a registry cleaner like CCleaner. If you are not comfortable with editing the registry then it is best to skip this step.

Do a malware check with some malware scanning programs on the Windows computer.
You need to scan with all programs because each program detects different malware.
Make sure that you update each program to get the latest version of their databases before doing a scan.

• http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware
• http://www.superantispyware.com/ - SuperAntispyware
• http://www.microsoft.com/security/scanner/en-us/default.aspx - Microsoft Safety Scanner
• http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page
• http://www.safer-networking.org/en/index.html - Spybot Search & Destroy

You can also do a check for a rootkit infection with TDSSKiller.

• http://support.kaspersky.com/viruses/solutions?qid=208280684

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

Having already wasted over four hours of my time to try to fix a piece of malware that only appeared after the update that I didn't ask for, and knowing that all other older versions of firefox still work I am really sick of the whole thing.

I have run Malwarebytes, Spybot, Microsoft scanner, and superantispyware, CCleaner already - all of which are meant to pick up this particular thing. I have AVG and spybot running constantly. I've also looked in MSConfig and there is nothing in the start up that shouldn't be running - only AVG & Teatimer (spybot).

My so-called infection hasn't spread to any of the other computers on my network, which is very suspicious and I am inclined to think that actually what has happened is that v18 has a bug with single core processors that causes these errors.

I don't understand what has changed so drastically with this tiny update that would make it impossible to even start up the browser compared to v16 or 17 which still run just fine. 
I've also found that every time I have reinstalled firefox on 16/17/18 - even when I uncheck the box to install the background updater, it installs it anyway and I think that is why it was still auto-updating even after I had told it never to. On my last install I deleted those files and for the last two days I've had no attempted update.

Don't get me wrong, I obviously want to fix this, but I have better things to do with my little free time right now.

Thanks for the responses, I will try running all the suggested programs again and see what I come up with over the next week.

astktkra.dll was picked up eventually, after running all of those programs and v18 has installed and opens without crashing now. I'm still suspicious of where it came from, but there's nothing I can do or prove about that, so I'm just glad it's fixed.

I still can't get the goodsearch toolbar to install though, even though it is still working on my laptop on v18 (that machine has had no problems). Just downloads and then I get a firefox pop up that says it couldn't modify the necessary file. Short of wiping all my firefox data, does anyone have any idea what could be causing that? 
I have delicious toolbar running just fine, all other add ons work fine, it's just this one particular one. 

I've contacted goodsearch in case they've changed the install file on their end, but it would be good to double check if there's anything else I can do to fix it.

See:

• https://support.mozilla.org/kb/remove-toolbar-has-taken-over-your-firefox-search-

• http://kb.mozillazine.org/Uninstalling_add-ons
• http://kb.mozillazine.org/Uninstalling_toolbars

It's not a problem with uninstalling. It's a problem with installing.

I've read through those links and several other articles, nothing was helpful at all with this problem or even mentioned it.

I have tried resetting my firefox, I have tried installing it in safe mode with every thing else disabled, and I always get the same problem.

I install the file, it goes through downloading the add on, asks for permission to install, and then I get a firefox pop up with the green puzzle icon which says 

'This add on could not be installed because firefox could not modify the necessary files'. And that's the end of it. The other add ons and extensions still work from other sources and from the site in question (www.goodsearch.com).