Find a windows machine and plug the harddrive into it.
then using the safely remove hardware feature of windows safely eject the drive. this will stop ntfs-3g complaining about a dirty unmount.
then bring drive back to your linux machine.
if this is a recurrant issue and you do not store files larger than 2GB on the drive (hard to satisfy that one these days) you may consider reformatting as FAT32 which is much more forgiving about dirty unmounts.
_________________
ArchLinux x86_64 - Custom Built Desktop
ArchLinux x86_64 - Compaq CQ50 Laptop
ArchLinux i686 - Acer Aspire One Netbook
ArchLinux i686 - Dell Presario ze2000 (w/ shattered LCD)
PuppyLinux, CloneZilla, PartedMagic, DBAN - rescue thumbdrives
Windows 7 (x86_64 desktop alternate boot)