I am a new owner of an EX3 and am using MxR cards. I am getting the restore media almost every time I shoot. I thought maybe it was down to me pressing play too quickly but i've slowed down my record finger and have been waiting til the light went green and it still happens. maybe its just something to do with me getting used to a new camera or is this a fault i should be more worried about.
It's probably the SDHC cards.
Please post EXACTLY what cards you're using.
When you buy SDHC cards, test by recording straight through including the slot change non stop. If the card gets a media error it's not safe to use. The next test is to do basically what you're doing, short records and waiting for the light to change back to green. Also delete a few clips along the way. Only when the cards can pass both these tests is it safe to use.
Honestly I believe it is the contacts between the cards and the adapter and the camera. Fortunately for me my adapter is a very tight fit in the camera slot on my EX3. My EX1 slots seems to be much looser and much easier to pull out.
I would insert and eject the card in and out of the adapter 40-50 times and re-run the tests Craig described. I would try and isolate this issue to either 1 adapter or 1 card. It will most likely be an adapter as they are just a conduit between the card and the camera.