Hi, people! I'm the original poster for this thread, and I appreciate all of your input. The only thing I really understood is the "uninstall" thingy for the KB308..., so I did that. After a reboot, I was able to open CM 2010. Hooray! However, I ran into the same roadblock the next day, tried the same fix, and then I COULDN'T open CM 2010. So I'm stuck again. Despite your good intentions, you guys are talking WAY over my head; I don't even know what a "patch" is! FWIW, I've got Windows 7.
Let me ask another question: If I take the CM 2010 disc out and try to reinstall the entire program from square one, will I lose all of my win-loss-rating data (like 500+ games' worth)?
Yeah, probably what's happening is that after you uninstall the KB308... update, Windows will soon automatically reinstall the update. Maybe the easiest thing to do would be to download the three CM patches, uninstall the KB308... update, then after the PC has finished rebooting, simply disconnect from the internet so that Windows can't reinstall the update.
Then, while you're offline, you'll have time to save your rated game data, uninstall/reinstall Chessmaster, install the three CM patches, and reinstall your rated game data. After you've finished all of that, you can reconnect to the internet and let Windows reinstall the KB308... update whenever it wants to. Then you'll find out if CM works after that.
...Let me ask another question: If I take the CM 2010 disc out and try to reinstall the entire program from square one, will I lose all of my win-loss-rating data (like 500+ games' worth)?
Before I go any further, I have to ask: You keep saying Chessmaster 2010, but I think you mean Chessmaster 10th Edition, right?
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I'm pretty sure that you WILL lose all of your rating data, unless you backup and save a few specific files before uninstalling/reinstalling Chessmaster. I THINK it's three files.
Let's assume that you played those 500 rated games in Chessmaster using the name Jim. If you go to this folder...
C:\Program Files (x86)\Ubisoft\Chessmaster 10th Edition\Data\Users\Jim
...you should find three files:
Jim.ppts
Jim.usr
Jim's Rated Games.PGN
Copy these three files to a safe place outside of the Chessmaster folders. (To your documents folder, or create new folders somewhere else on your hard drive.) To be on the safe side, you might want to copy these files to two or three different places.
Then it should be safe to uninstall/reinstall Chessmaster. After reinstallation, start up Chessmaster and create a new player named Jim. (It has to be identical to the old name, and it's probably case sensitive, too.) Now, exit Chessmaster.
Now, go back into the "C:\Program Files (x86)\Ubisoft\Chessmaster 10th Edition\Data\Users\Jim" folder, and I'm guessing that there will be three new files with the three file names above, but since you haven't played any games after reinstallation, the files should be relatively smaller. Delete those three new files, then copy the three files that you previously saved back into the "C:\Program Files (x86)\Ubisoft\Chessmaster 10th Edition\Data\Users\Jim" folder.
Now start up Chessmaster, and if I'm right, you should still have all of your rating data.
I can't absolutely guarantee that this procedure will work, because I didn't actually uninstall and reinstall Chessmaster. However, I did do some testing that I think indicates that the procedure should work.