Mmmm, it might suggest that the partition table is corrupted.
fdisk can see the partitions but Gparted can't. You can manually remove, format and create new linux partitions using fdisk on the command line if you feel brave enough.
If you are going to blow away the current Mint installation anyway, I might be inclined to use the partitioner in Vista to remove and format the linux partitions and then fix the MBR using the Vista recovery console: http://support.microsoft.com/kb/927392
Your partitions were clearly seen when you first installed Mint, so perhaps getting the drive back to that point might help..?