i don't know if this is gona fix it or not but you can always try....

well i had to same problem but with a 8gb card and some other cell phone...

the thing was that the card format (Like it is basically FAT or FAT 16)

So for that try fromatting it but not on the phone or directly from the card reader by right clicking the drive icon and formatting it

Format it with Panasonic SD Formatter......

it might be available online for to download a very small but very effective software for formatting Memory cards...

I hope it solves the problem....

If you can't find the SD formatter email me...
darguzar@yahoo.com