Is it normal for the microdrive to get warm?
You don't know what "warm" is until you have used the microdrives in a laptop PC-Card slot! :idea:
When installed in theses PCMCIA slots much more power are available to them as well as the wider 16/32-bit data path make them almost impossible to hold when ejected -> All the drives have internal temperature sensor that will shut them down automatically and are designed to go back on-line when allowed to cool...
In your case the camera shuts down before the microdrive: In the case where the microdrive shuts down first, you would see either invalid media or no CF-card until the card cool off.