The registration is permanent, and the activation is valid unless you change hardware (move MEP to a different computer, for example).  I'm guessing the close all programs message is the message MEP typically puts out when it hits a corrupted memory situation, or a necessary library file (dll) gets corrupted on the hard disk drive.

You might try the old uninstall/reinstall routine. Uninstall MEP, reboot and install it again.

Good luck,

Tim