I run firefox and it crashes on a regular basis. I'm thinking of ditching it.
Getting the same issue as you with the black bar over the "upload file" link.
I get a script window popping up saying stop script. I stop it, then hit the keyboard hard in anger. Helps me a lot!
To be fair, its not Firefox's fault. Its Adobe's fault. Flash has been plagued with bugs, stability and security issues since its creation. Remove Flash and all problems will be solved.
Flash isn't needed in modern web. File upload works perfectly without it. Most streaming services today support video without Flash. Any websites that require Flash should die in web development hell, where old IE is.
What happens to me is that I check my email sometimes not often and have several alerts, I click them one after another so I get maybe 5-10 tabs loading (Firefox). Or I go to Watched Threads and right-click open in new tab and sometimes (not always) when I load too many and they are all spinning, it freezes and then 30 seconds later I get the pop-up saying Shockwave Flash crashed and should I stop plugin, etc. Click, wait 30s, pops up again, this repeats endlessly (I've only had it unfreeze once actually) and I have to just ctrl-alt-del and kill firefox manually.
I disabled the flash plugin and it seems to have stopped. Happen here and on any other XF forum I frequent, no rhyme or reason as to why or when. I can go slow and load one tab at a time and usually that works but there are times when I'm loading 15 tabs and it doesn't freeze and other times when 1 tab will freeze it.
I picked up that it's flash from several comments, I wasn't intending to say it's a bug with XF, I guess just venting frustration. It seems to me that if this were a common issue and causing crashing left and right, they'd friggin fix it.
So now my question is (and this may have already been answered in multiple places, sorry....) what is flash needed for, and am I "missing out" on some "experience" on XF sites by disabling it?