Well, I had a theory last night, and tested it, and now I'm even more confused than ever.
I have two machines, as I mentioned above. Both are almost identical in hardware and software configurations (I'll run through the list in a moment), and until last night, both exhibited the problem. My theory was that the error had something to do with the Media Scheduler and the "Reclaim File Associations" option that appears on the File Associations options pane. I'm still not convinced that the problem is not related to that, but my results were mixed. Does anyone who is getting this error typically run with the Media Scheduler (and Reclaim File Associations) selected? I know that at least Alex and I do not.
My HTPC has exhibited the error with every build since .236. I had been testing each build, and then reverting back to .236 on that machine, but I last left .244 installed (since the error wasn't as obnoxious on that build). On my "Main PC", I had only tried .240 once, seen the error, and then reverted back to .236 (and kept it that way). Actually, because I am in the process of moving, my "Main PC" was torn down until last night.
Anyhow, my theory was that the Media Scheduler and/or File Assoc. Reclaiming was causing the error if it wasn't selected when you installed a .240+ build. So, on my Main PC, I selected the File Reclaim option from inside build .236 (which started the Media Scheduler) and then upgraded to .245. No error! So far, so good. So then I de-selected the Media Scheduler and File Assoc. option, got the Media Scheduler to actually close and stay closed (which involved deselecting another option in Options - General), and then opened MC and the Options, hoping I'd see the error. Still no error. So, I thought it must have to do with actually having the option de-selected when you perform the upgrade. I reverted back to .236, made sure the option was de-selected, performed the upgrade to .245 (rebooting inbetween). Still no error! Somehow, I seem to have fixed the error on my Main PC. So, I figured I would perform somewhat of the same procedure on my HTPC and give that a whirl...
Using a similar procedure, I couldn't get the error to go away on my HTPC. However, I also couldn't get the Media Scheduler to run by selecting that option during the Install procedure. It seemed that I needed to actually select the option from inside the Options panel (as I did with my Main PC) from inside the .236 build.
Unfortunately, I can't access this option on my HTPC due to the large font problem I mentioned above (please make the options form resizable -- I don't care that it "correctly" resizes proportionally, just let me make it bigger so I can get to those other options -- or make it scale the form correctly for large fonts). I thought about disabling the large fonts in the persuit of knowledge, but I ran out of time and patience with my wife (who wanted to watch the most recent episode of Deadwood).
Either way, the procedure I performed on that machine was not identical (I wish it could have been, but such is life). I initially had .244 installed on that machine. I tried upgrading to .245 but selecting the Reclaim/Media Scheduler option. No dice (still had the error), however I actually had the error before being allowed to select that option, so maybe that broke it... As I mentioned, the Media Scheduler did not actually start when I selected this option, so it seemed like the option wasn't "taking". I reverted to .236, selected the option during the install. Rebooted. Ran MC (the Media Scheduler actually did run this time). I then upgraded to .245. Still got the error.
Argh!!! As I said, I can't even confirm that the Reclaim Assoc. option is selected on my HTPC (even though the Media Scheduler was running) because I can't see that option in the dialog. So...
More confused than ever.
Machine details:
MainPC: Athlon XP 2000+, ASUS A7N8X-X (nForce2), Sapphire X800XL AGP (with dual VGA display extended desktop), 1GB DDR400 RAM sync with processor (CAS2 timings), Creative SB Audigy2, Promise ATA133 PCI Card, and a big pile of hard drives, Intel Pro Gigabit LAN PCI.
HTPC: Athlon XP-M 2600+ (not overclocked), ASUS A7N8X-E Deluxe, ATI AIW X800XT (TV primary, VGA monitor secondary cloned), identical RAM to Main, onboard sound (I'm saving for a M-Audio), Promise S150 SX4 SATA RAID PCI Card w/ 128MB PC133 RAM, another big pile of hard drives, Intel Pro Gigabit LAN PCI.
The software outlay on the machines is really almost identical. Both are XPSP2 with fully up-to-date drivers. The Main PC has some games the HTPC doesn't have installed, and the HTPC has the DVD Player/Codec from ATI's MMC, TV, and Guide+ installed (whereas the Main PC only has the Video In tool installed from ATI's software).