The End-Y safety interlock system for E-stops had a failure.  This shut down the ALS and SQZ lasers.  An input module that monitors the VEA Entry Estop lost one of two channels.  This caused and error in the system and thus shut down teh lasers.  We would have been down for an hour except we struggled getting the system back up.  It appears that the module we tried to replace teh bad unit with also had trouble.  This module was taken from a test stand so we are not sure of it's pedigree.  We again swapped the module with a replacement and the system returned ot normal.  All lasers restored by noon.