Okay, long story short, I was on YouTube looking up differences of N64 games between the original and their Virtual Console versions, as I have some Wii Points I would like to use and was considering what to use them on. (Holy crap at the differences on Starfox 64!) The only things I had going on the taskbar at this time were Firefox, its library history, and the task manager.
During this, one of the related videos was "Phoenix Wright: No Shit Sherlock", to which I went "Oh yeah, I remember those. Let's look at a couple of those for a laugh" (mousewheel click)
And that's where things went weird.
Not only did the mousewheel click open a new tab for the Phoenix Wright video, but it also loaded it on the current tab. I had to hit Back to get back to the previous video. On the new tab, where I wanted to watch more Phoenix Wright parodies, when I tried to click on another link, it was immediately stopped. I kept clicking, and it kept stopping. Then I started getting a ton of new Firefox windows (or a new window full of tabs, not sure) of various websites in my history, and I'm in a clicking frenzy trying to close them all.
I tried to get to my task manager so I could just close Firefox that way, but I couldn't get it to stay as the thing on top once I got to it, so I decided something is definitely wrong and turned off the computer by holding down the power button.
I wait about 10 seconds, reboot normally, and do what I normally do and try to open Task Manager as soon as I can. (I always do this.) It won't let me right click. I see the menu trying to open but then it immediately disappears. That has never happened before.
I get to the Task Manager using Ctrl+Alt+Del. I don't see anything unusual.
I have Norton AV and Norton Utilities. I cleaned the registry and internet traces, and did a full scan. Scans only turn up the usual stuff like tracking cookies.
Before doing the full scan, I check Norton's history, and it's telling me that the computer was off for about three hours before this moment, which isn't true because it's been on for the last 12 hours.
During the full scan, I get a notice from Norton basically telling me something is using a little more of the computer than it should. It's "lsass.exe", and the only thing that appears to be odd according to Norton (because it's in red text) is that the "Disk Write Activity" is at 1MB. CPU, Memory, Handles Count, and Disk Read Memory are all at Normal.
I haven't noticed anything else unusual. There's nothing new trying to put itself on my C drive or anything like that. (That happened once, but Norton stopped it.)
Any suggestions for what should I do to make sure there isn't anything wrong with my computer?