Microsoft can't explain why this might be happening, though Spanbauer theorizes it may have something to do with earlier this month, which overwhelmed the company's servers. This may have caused some updates to not fully download, which in the past has caused problems with update notifications. As S.S. notes:

At this point, I'm unable to make the behavior reproducible or demonstrate the exact conditions under which forced installs occur. Until a better explanation of the aberrant update behavior is provided, however, I'm calling it an unpatched bug.

At this point, my thoughts on Microsoft browsers are well known (and alternately loathed or lauded). But what bugs me isn't IE8's security holes -- it's the performance suck. I've never gotten a Microsoft browser to perform as nimbly as Firefox or Chrome; opening more than a handful of tabs turns my computer into a mastodon stuck in the tar pits. And I'm not alone. Reader Charlene says:

I'm about to switch back to IE7 on one of my computers. It's an older computer with only 1GB of memory. IE8 creates a separate process for EACH tab. After opening my normal 5 windows with 6-12 tabs each... oops, didn't get to the 4th window. IE8 hung. Have to reboot... Now I have to turn OFF the computer because it won't shut down on its own.

Exactly. Of course, your mileage may vary. But one of my favorite definitions of insanity is doing the same thing over and over and expecting different results each time. I've had the same experience with every Microsoft browser since IE3.