I have had the same problem and it is mainly due to Windows and its approach to USB HDD's. I am using Windows XP and a 500 GB Buffalo external USB 2 HDD with a "Turbo USB" software utility. I really do not know how to properly unmount the drive, especially when the "Safely Remove Hardware" notification icon is not listed in the notification panel (bottom right of screen), why this is randomly shown is another mystery awaiting solution; but since disabling the "Windows Indexing" feature things seem to be more consistent.
Now I recently had the cannot mount error when trying out the Linux ZORIN distro the "Linux"error message much more informative that b----y windows is as follows:-
External Hard Disk Error would not mount in Linux Zorin 2/04/2013
Unable to mount 500 GB Filesystem
Error mounting: mount exited with exit code 13:
The disk contains an unclean file system (0, 0).
The file system wasn't safely closed on Windows.
ntfs_attr_pread_i: ntfs_pread failed:
Failed to read NTFS $Bitmap:
NTFS is either inconsistent, or there is a hardware fault, or it's a SoftRAID/FakeRAID hardware.
In the first case run chkdsk /f on Windows then reboot into Windows twice.
The usage of the /f parameter is very important! If the device is a SoftRAID/FakeRAID then first activate it and mount a different device under the /dev/mapper/ directory, (e.g.
Please see the 'dmraid' documentation
for more details.
Since getting this have gone back to the Windows XP computer and eventually after a lot of "trial and error" managed to get the Buffalo drive mounted and able to access the files on it.
Can anybody help with advice on what to do next?