Disable HTTP3 support by disabling 'network.http.http3.enabled' key in about:config and then restart Firefox. Worked for me.

Hi

I appreciate that you may have done this already, but please can you restart Firefox which should resolve this issue.

Earlier today, Firefox became unresponsive due to a change in defaults by a cloud provider which triggered a Firefox HTTP/3 bug. We disabled the configuration change and confirmed this fixed the issue.

Hi… Yep, I did all that… but still had the issue. What I forgot to mention is, also, when opening up Firefox, got a pop-up info saying that Firefox was already running, and that I needed to close it, which I did not. This said, I uninstalled 96.0 and reinstalled 95.02… put the updates to manual (being asked) and will wait ‘til the bug is fixed! ;-) Thanks guys, and have a good one!

"We disabled the configuration change and confirmed this fixed the issue." ... ah, so all should be good, correct?

Yes, you should find this is all okay now.

Yep!!! All good! Cheers!