Hmmm I've never seen a shoot-outable light in HL before. I guess this is why.
Something about the func_breakable targeting a light's name must be bugged in the engine.
Try adding a middleman:
1. Make the func_breakable, have it target middleman
2. Make a multimanager, name it middleman
, unclick SmartEdit and add the key/value pair breaklight
3. Make the light with the name breaklight
Also: I only check the forums about once a say so stop whining when I'm not around.