As far as I understand it the original SDIO standard only went up to a max of 2GB. The current 4GB cards are either hybrids (stacked 2GB cards) or use an updated standard that may or may not be compatible. Personally, I'd go for a larger CF card for the 2210, there aren't any compatibility issues there.
"A planner is a gentle man, with neither sword nor pistol.
He walks along most daintily, because his balls are crystal."