I've had no problem with my R09 - 4 gig cards are suported with the 1.20 firmware, I think, so anyone who hasn't updated yet may well find that helps.
i agree, by all means update your firmware!
4gb SDHC cards are supported by firmware 1.20.
the transcend 4gb non-SHDC card works, somewhat, but not without lots of bugs: corrupt files, files with misreported sizes, et al.
if you own a non-SDHC 4gb card, you'd be better off cutting your losses and pitching the card. buying an SDHC card will set you back a few more dollars, but it won't cause you any headaches down the road.