Periodically the the default OS cursor will appear in the top left corner and when it appears it causes the game to minimize when I click. Used to be merely an annoyance, but now it's causing the game to crash after installing some of the streamlining mods and such(I find myself regretting that decision after it messed with my LOD ranges and texture alpha layers).
It seemingly has nothing to do with my graphics card or processor since I found a similar post elsewhere that specified an Intel/Nvidia(I run AMD/ATI) machine was getting the same issue. Has anyone encountered this?

running vista, or win7? turn off the sidebar, and disable visual themes while playing.

I get something like this when Microsoft Security Essentials downloads and installs malware definitions. My solution is just to do an update of the definitions before running Oblivion, so it won't interrupt.

I'm running windows XP and I have purposefully disabled via various methods the autoupdater. So it isn't the updater.

Something I think is of note though is that I did install the K-Lite codec pack and now when ever Oblivion is running the AC3filter keeps popping up(Seems like once for each time I talk to an NPC) in the bottom right side of the task bar. I would think this unrelated, but it does strike me as odd, and only of negligible concern.
I also run skype, xfire, raptor, file incinerator, and the logitech G15 keyboard software. Should have occured to me earlier, but I'll try disabling xfire and raptor since those pop up with ingame messages.

Confirmed, seems that programs like this that have an ingame overlay do this. That's one for the FAQ since Xfire is a rather widely used program.

I thought that xfire had some flavor of update, to prevent such occurences? Or, there was some setting or other that you could change.....

For XFire:

-Find your desktop icon for Oblivion
-Right click and go to "properties"
-Go to "compatibility" tab and check "disable visual themes"

then try...

Will do. This would be something for the FAQ, since xfire is rather widely used.



Also Tig an observation, the triple period at the end of your post gives an impression of condescension. Thought I'd help you out there.

Did the trick, thanks guys. I highly recommend you add this solution to the unofficial FAQ.