I got a new MacBook Pro 15" at the end of November, and just got around to setting it up properly and putting it to use.

Today, I plugged in my SanDisk SDAD-109 ExpressCard reader to transfer some video and pictures from my HD Sanyo camera/camcorder. After I was halfway through the transfer, I got the "Device Removal" error that you get when you remove a card without unmounting it, even though I had not touched the card. A second later the card remounted. It then proceeded to randomly mount/unmount as it saw fit.

In trolling the forums, I saw that I was not the only person with this issue. Apparently this is an intermittent problem, since some people have problems and others didn't. The issue was not restricted to one particular type of ExpressCard reader - it seems that it has affected people with both SanDisk and Griffin Technology models (and possibly others). One guy said he sent his Mac back for a new one and that his new one didn't exhibit the same issue.

Anyway... I was able to fix the issue by simply calling AppleCare, at which point they recommended I reset the PMU (which they walked me through). I listed the steps for how to do this in detail on the support forums, so feel free to link over there for the resolution. I can't find a way to link directly to my comment, so just scroll down to my post at Dec 13, 2008 11:15 AM after you link over (it's listed under my name).