Please ignore albert0, he talks more crazy than sane stuff.
About your problem, one solution you can still try is to simply try another input plugin that supports Memory Paks et al, like the N-Rage input plugin (which is better than the default Jabo's DirectInput anyway). Google it or check the plugins forum.
The bottom line is that the MemPaks should work just fine after you've enabled them in the Controller plugin configuration window. Same with all the other swappable Paks.