Sessions & Tracks : Mac HFS+ Disk Support Option (Windows Only) : Mac HFS+ Disk Support Warnings : Volume Check

Volume Check
Whenever a disk is mounted, Mac HFS+ Disk Support checks the disk to see if it was properly unmounted the last time it was used.
If there are signs that it wasn't unmounted correctly, Mac HFS+ Disk Support displays a warning so that you will know there is a risk that the disk was improperly unmounted.
If Mac HFS+ Disk Support displays a Volume Check warning, do one of the following:
*
*
Mac HFS+ Disk Support will only mount such a drive in Read-Only state, so it cannot be used to record in Pro Tools.
Note that this warning does not mean that the disk has been judged to be corrupt; it merely means that there is a significant risk, and that the disk should be remounted and then correctly unmounted on a Mac system before reconnecting it to a Windows system.
If the problem persists, the disk should either be repaired or reformatted (using Mac OS X Disk Utility) in order to avoid future problems.