Please update your SD Card driver with the one found at the link below and you should be good for any card up to 8GB.
Not to be rude but this fix is well documented so you might try a search before posting.
http://forum.ppcgeeks.com/showthread.php?t=9713
--- JPMinAR ---
HTC Titan/Mogul (6800)
HTC Apache (6700) x5
HTC Blueangel (6600)
Toshibah 2032
Running Custom Sprint 2.17
Radio 1.43