[CentOS] External USB Hard Drive mount problems

Hi Folks I have a number of external USB enclosures with hard drives in. Some are IDE and others are SATA drives. I'm running CentOS 5 + all updates. Recently when I plug in an external drive I get the message "Invalid filesystem type. I have install the NTFS-3G bits stuff and reformatted the hard drives with FAT32 but still get the same error message. This started after an update (not shore which one,) as I had been able to copy files to / from these disks before. I have turned off selinux and had a look at my fstab file, but can't see any thing obvious. Can some one point me in the right direction to debug this please? Regards John