I bought a refurb'd MacBook from apple.com. It's been great. But now I have a minor support issue and noticed that the serial number on the MacBook (About this Mac) is different than the one on the invoice. Doh! Seems like someone packed the wrong MacBook in the wrong box when I bought it. Of course, AppleCare can't help me until I get this situation rectified with Sales Support.

Apple often changes the serial numbers on computers when the refurbish them. Unfortunately, it's been known to cause problems when warranty issues arise.

I had a similar issue with a computer I purchased from a retailer where they had keyed the serial number in incorrectly. All I had to do was fax my receipt and a screen shot of the About this Mac screen and they correct the issue with my Apple Care.