What OS will be running on this SD card? I find it is usually best to create partitions using whatever OS's native partition tool. Or was there some special need here such as re-sizing an existing partition?
If the OS native partition tool gets confused, the drive may need to be wiped first. In that case, this Wipedisk tool might help:
http://www.lo-tech.co.uk/wiki/WipeDisk just be sure the drive you want to wipe is the only one attached as it is too easy to backwards things get. An alternate method I find handy is to use Norton Utilities 4.5 to manually edit and clear physical sector zero - when something goes wrong it is easier to see what happened.
Anyway, with a Linux partition tool all you need to do use use a Linux "Live CD" (or USB stick). You don't need to install it or do anything, just pop a live CD in the drive and if it recognizes your hardware then you wind up at a desktop where you just run the partitioning tool. Although in the case of partitioning you might want to unplug any hard drives you don't want to alter first just in case.