In one case, simply trashing preferences for Pro Tools LE fixed this problem.

To trash ProTools preferences in Mac OS:

In the Macintosh HD, go to Users > (your user name, aka "the house icon") > Library > Preferences.

Delete the following files:
- com.digidesign.protools.plist
- DAE Prefs (entire folder)
- Digisetup.OSX
- ProTools...v6.x Preferences (this may be either ProTools LE or TDM, and any version, such as 6.4 or 6.9).

Empty the Trash after trashing preferences and/or databases.

To trash ProTools preferences in Windows XP:

Go to: My Computer > C: > Documents and Settings > (your user name) > Application Data* > Digidesign.
Delete the file entitled "ProTools...v6.x Preferences.PTP" (this may be either ProTools LE or TDM, and any version, such as 6.4 or 6.9).
*If the Application Data folder is not there, go to: Tools (in the menus at the top) > Folder Options > View, and select "Show Hidden Files and Folders."

Go to: My Computer > C: > Program Files > Common Files > Digidesign > DAE. Delete the entire "DAE Prefs folder."

Empty the Recycle Bin after trashing preferences and/or databases.