"Acrobat failed to load its Core DLL" error in Reader XI, 11.0.2--how to fix??

Windows 7 machine.

This error just started occurring yesterday to me; the fatal error message box appears with the subject message

1) if I try to start the Adobe Reader application, or

2) try to open *any* PDF.

I've tried the following remedies:

1) Uninstalling Reader XI, reinstalling Reader XI, then restarting the computer.

2) Control Panel-->Programs-->Programs and Features-->rt click Adobe Reader XI-->Change; after it's finished, restart computer.

These had zero effect; what are other suggestions?

Thanks.