Is This Legit?
I've seen it a couple rare times as well. I think 3 of the 5 times that I got it, I ended up with a sound loop, but was still able to play. One time it played normal, and the other time actually did crash and I has to re-load the client.
When I had the sound loop, I was near the end of a successful MoKhan TF, so I turned off my speakers so I wouldn't have listen to it while we finished him off, then I restarted my client myself.
I don't do any we browsing or any crazy stuff on my gaming PC at all, so I was posative it was legit.. either part of the game or the OS anyway. (I do everything else on my laptop on the side instead).
It is indeed legit and unless you're in the middle of something that shouldn't be interrupted you should hit yes to submit a report about it as this is usually indicative of a MAJOR error somewhere in the code and every report on something that threatens to cause a hard crash allows the devs to get closer to pinpointing the source of the problem.
I was doing a Mothership Raid and this popped up:

Never seen that in the 6 years I've been playing, so I was very wary. I tried to just X out of it but it wouldn't let me. Weird thing was, I just clicked back into the game and played as normal. I was just worried it was some kind of scam trying to get into my account or something. Anyone know if that is actually a pop up from the game?
Shadowblaze - Lvl 50 Dark/Thermal Cor, Alexander Kalsoa - Lvl 50 BS/Regen Scrapper, and a whole bunch of other Alts. Global is @Shadowblaze.