We're not exactly sure why this happens, but we're sure it has nothing to do with your Glyph hard drive. Here's how to fix it: In Pro Tools, click on the "Window" drop down menu, and select Workspace or Show Workspace from the drop down menu. Find your Glyph drive in the list on the left, go the A column and click on the letter there. It should be set to Record, if it's set to Transfer or Playback, you won't be able to record to the drive.
If Pro Tools does not allow you to change it to Record, trash the Digidesign Databases folder on all of your drives, inlcuding the system drive, then reboot. Open the session and try again to set the drive to record. If you still cannot set it to Record, trash the Pro Tools Preference file (USERS/username/library/preferences/Pro Tools preferences) and reboot. Once you trash the preferences file, Pro Tools will be set to default preferences.
Here is a handy tool for trashing preferences called the Pro Tools Prefs & Database Helper.