These images are included with original error submission.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

If it works in Safe Mode and in normal mode with all extensions (Firefox/Tools > Add-ons > Extensions) disabled then try to find which extension is causing it by enabling one extension at a time until the problem reappears.

Close and restart Firefox after each change via "Firefox > Exit" (Windows: Firefox/File > Exit; Mac: Firefox > Quit Firefox; Linux: Firefox/File > Quit)

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

I'll give it a try.

It happens very irregularily, so it may take a couple of days for me to report back.

hello cdnkevin, other reports by users indicate that it is caused by the McAfee SiteAdvisor extension - so keep that disabled for a while...

McAfee SiteAdvisor often (everyday) crashes for me. I hate that thing. I've gone ahead and specifically disabled it in Safe Mode, and will continue with all others disabled to see what else there might happen.

I had this same problem, right after the update to Firefox 27.0.1. It seems to have been fixed now that I disabled the McAfee SiteAdvisor 3.6.5 extension. (I did this by going to: 1. Firefox 2. Add-ons 3. Extensions 4. Clicking "disable" after McAfee SiteAdvisor 3.6.5.) Now I just have to remember to re-enable it after the next Firefox update (which I'm sure I won't remember to do). I really wish Mozilla could get all the bugs out before offering Firefox updates. Almost every time, after an update, something is wrong with my browser.

I e-mailed their support group who gave me the exact same instructions. I went ahead & disabled the McAffee extension. So far so good. My concern is whether my computer is at risk by this process. I have an anti-virus program installed on my computer that works just fine. Just wondering.

Thanks for your insight.

It's been a couple of days since the SiteAdvisor program has been disabled, and I haven't had the issue again.

Mozilla seems to have a lot of problems with anti-virus programs. They have a support page that lists problems with nearly all of them, but the implication is that it's the anti-virus program that's the problem, not Firefox.

Funny, but these problems don't occur with Chrome or Internet Explorer. The real problem is pushing new versions out the door without sufficient testing and/or ignoring incompatibilities because they're inconvenient to deal with.

Well, it has been almost two months since I reported this issue.

I have to say that, since I've disabled the "McAfee SiteAdvisor Extension", I haven't had this error again.

If I were a computer programmer, I'd help write code to fix this problem, but I'm not. Does anyone know of any patches in development to fix these types of issues, so that this problem can be solved?

hey, if the error is caused by the extension's code then it will be up to McAfee to fix that - please contact their support site at http://www.siteadvisor.com/support/index.html to report the issue. thank you!

Hi philipp,

Thanks for your response. Pardon me for asking this question, but how can I tell "if the error is caused by the extension's code", and not due to a problem in Firefox? I would never expect McDonald's to solve a problem I had in a Burger King store.

I don't have much computer coding experience, and it's not reasonable to report this issue to companies at random (ie. how do I know it's not a chipset problem? Vista OS issue? etc?).

How can I tell?

Several months ago you helped me solve a problem w/ an error message that I would occasionally receive when I was on the internet. Two days ago I received a different message: Type Error: "w is Null". Any suggestions? The message from a few months ago was (I think) Type Error: "oE is Null" Thanks in advance for your expertise & insight on these matters.

gbs

Did you try to start Firefox in Safe Mode?

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Hi gbscoggin,

I'm not sure who you're referring to when you say "you", but if it is me, disabling the McAfee add on gave a temporary fix to my problem, but I did not have an error indicating "w is null".

Doing a quick search came up with this: https://support.mozilla.org/en-US/questions/992074

Thankfully Corel gave the same advice, and beyond that (unfortunately) I have no further suggestions.