The problem is (I think) with the GP32.  Supposedly, SMC hardware is backwards compatible, but not forward-compatible.  For instance, if you got a device several years ago when 64mb was the max, it wouldn't read the 128mb cards when they came out.  Apearently each different size card uses a completely different addressing system.  If support for a certain addressing system isn't built into your hardware, you can't use cards with that system/size.  I would have posted this before, but I was kind of hoping I was wrong (and abbibi had already ordered his XD adapter).