Make sure you are not blocking content.

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

One issue that seems more common lately is Firefox's Tracking Protection feature. When it is blocking content in a page, a shield icon will appear at the left end of the address bar next to the padlock icon. This article has more info on managing this feature: Tracking Protection {web link}

Thanks but when I'm in the middle of entering often complicated site information and it appears to stall, don't want to have to quit the browser entirely to enter safe mode, which, btw, would remove any protection afforded by NoScript, uMatrix, or uBO, or anything else -- even though everything would be allowed that's needed to be allowed in any of those.

Will take into account the tracking protection feature you mention, if it appears it might be responsible on any given occasion (although needing to pay attention to that could be almost as distracting as having to enter safe mode), but as said earlier, this seems to be something intrinsic to Firefox.

Don't expect this question to find a real solution, except with Mozilla doing a fundamental rewrite of the code for whatever the real underlying issue is.

https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode

Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes). If the problem goes away, that tells us one thing. If it does not, that tells us something else.

I already know what Safe Mode does -- that's basic, generic troubleshooting. My point is that with all add-ons disabled in Safe Mode, NoScript (which can defeat possibly malicious scripts), uMatrix (malware protection via hosts files), uBO (which might prevent exploit containing ads) etc., and then try to supply new credentials -- which might be highly sensitive -- to a site of some kind, I will be without any protection -- which will allow anything and everything to run without hindrance. At that point, I might as well use Safari, which is what I usually do when I finally become aware of the presence of an "I'm not a robot" recaptcha with Firefox.

But it's usually only when a site stalls out that I discover the presence of a recaptcha, after having proceeded through any number of arduous steps, that I know to switch as soon as possible to Safari. That's why this can be so exasperating. Just happened to me again yesterday, which is why I'm feeling so pissed at Firefox right now -- otherwise my browser of preference.

As I said, I don't really expect a solution. I appreciate the help you're trying to give, but I suppose I should probably submit a bug report instead.

Have you tried disabling the ad-blocker for that site?

FredMcD said

Have you tried disabling the ad-blocker for that site?

Think I've tried that on other occasions, didn't work. Can't test current one with adblocking disabled, since that would require creating new unwanted login/account creation. Can't remember for certain, but may even have tried that with this current one, along with allowing everything possible in NS, uMatrix etc.

Basically, just wish I spot the presence of the recaptcha earlier on next time, before I waste a lot of time and effort entering information in various steps, and go straight to Safari.

I assume you don't experience this problem?

LX237i said

I assume you don't experience this problem?

No, but this is most likely due to tracking protection. You have to turn it off for the specific site as it was told before.

TyDraniu said

LX237i said

I assume you don't experience this problem?

No, but this is most likely due to tracking protection. You have to turn it off for the specific site as it was told before.

Will keep that in mind for the next time.