Apple ID and password nightmares

Question

For years I've never had trouble with my Apple ID and password. However, I am amazed that I was able to log on here to the discussion board after what I've been going through the past 36 hours.
Yesterday, I was trying to renew my MobileMe and it would not accept my ID and password. I did an online chat and learned that my Apple ID and password for Mobile Me are DIFFERENT than the Apple ID and password for my computer--so what I had recorded and stashed away for safekeeping was actually WRONG, apparently, although I have used it over the past year to access MobileMe (weird). That was an easy one to figure out with tech support--I just had to switch to a different "user name" but the password turned out to be exactly what I had written down all along.
However today I hit another bump. I installed a new battery last night in my computer, so I was trying to make sure I calibrate it correctly. I found an apple support article describing how to do it. It had a handy email icon so I thought I would email the article to myself for reference. In order to email it, I had to enter my Apple ID and password. It would not recognize the password I've been using for years. Instead I get an error message that says: "Language code supplied is not valid." It gave me the option to change my password, so I did, and I received an email notification that the password had been changed. So I tried again to email the article and went through the Apple ID and password form again. Again it rejected my password. Again, I get an error message saying: "Language code supplied is not valid." Oddly enough, after that, I went to this discussion board and was able to log on using my old Apple ID and password just fine.
This is starting to scare me because, first, my MobileMe apple ID and password appear to have changed from what I recorded originally (although I was able to ferret out something that works now). And now my apple ID and password for my computer seem to only work sporadically. I'm afraid I'm going to get locked out of my computer altogether, and since I'm self employed and this is my work computer, that could be devastating. My AppleCare just ran out, so I'll have to pay for any service calls, apparently.
Anybody have any ideas about what's going wrong?
FYI, I installed Snow Leopard a couple of weeks ago as well as all of the updates. Seemed to work fine until I noticed it was taking my computer at least a minute to go to sleep when I close the lid or use the pulldown menu. Also, my external hard drive used for Time Machine no longer shows up in my "Devices". However it still backs up okay and the icon does appear on my desktop. Now my Blackberry stopped showing up in "Devices." So I went to the Genius Bar yesterday. They suggested I re-install Snow Leopard and all of the updates again. So I did. Still, external drive doesn't show up in Devices. I tried dragging the icon from the desktop into the Devices column and it showed up there and the little wheel was spinning as the Time Machine was doing its thing. But when it came time to eject the hard drive, I couldn't eject it using the little triangle anymore. I had to go to the desktop and drag the icon to the trash.

Answer 1

I promised to write back if I had some solutions to the problems. Here's what I've learned since my Friday and Sunday visits to the Genius Bar.
1. Yes, your "Apple ID" and your "MobileMe Apple ID" can be two completely different things, even though Apple only identifies them as "your Apple ID," so keep records of both (apparently, I tied one to one of my email addresses and the other to another one, but didn't record it properly). You can make them the same, I suppose, if you choose.
2. The reason that my Apple ID wouldn't work to allow me to email the apple support article is that the email function is NOT AVAILABLE to non-Apple personnel. You have to have a special Apple-issued ID in order to use the email function (the Genius Bar told me I was not the first to come in with this problem). Perhaps, instead of an error message saying "Language code not recognized" and a prompt to let me change my password, an error message saying "this email function available only to Apple personnel" would've been far more helpful. Apple, you should fix this since I'm not the only one who has needlessly gone to the Genius Bar for this.
3. The second Genius was still stumped about why my external hard drive wouldn't show up in "Devices" and could only be ejected by dragging the desktop icon to the trash. But he said as long as it would mount and still do backups with Time Machine, it was probably just a little glitch that I should consider learning to live with (although he offered more diagnostics). I agreed to live with it. However my husband had a brilliant suggestion--try completely unplugging the external drive from the AC and let it rest for a bit, then plug it in again. Just tried that and it worked--the device now shows up in "Devices" for the first time in a week or so.
4. Haven't tried plugging in the Blackberry to see if it shows up Devices now. I'll wait until I need to sync again. Worst case scenario is I'll just unplug it to eject it like last time. I know that's not great, but it may be my only option. Can't wait to get the iPhone (I'm Verizon).
5. Computer is now going to sleep on command. Not sure if it's a result of some of the diagnostics from my Friday Genius Bar visit or a result of a completely new reinstall of Snow Leopard.
Thanks to all who posted suggestions. I'm keeping the message about how to zero out the hard drive--I might do that at a later date just to clear the decks once and for all. I appreciate the suggestions about how/where to do multiple bootable backups.