It seems that a number of people have this problem (based on searches that bring people to this site) so here are a few links which may be helpful:
Apparently, Samsung has manufactured a range of dual voltage RS-MMC cards. They put out a news release in March 2004.
The bottom line is that you should be careful when you buy a RS-MMC because it may not work. Check it is a dual voltage card first and that it will work in your Nokia 6630. This applies to all phones that use memory cards – make sure you are buying the right one for your phone. You don’t want to wind up with an expensive card you can’t return and have no use for.