I have now, on several occasions, experienced not being able to cast earth spirit's boulder smash on a valid target. I click the skill (either using the short cut or moving the cursor), which is then highlighted, and click on an enemy hero. nothing happens, except the skill is no longer highlighted. I can then try again, with the same effect. the few times it has happened, the problem is gone 10 seconds later. I have experienced it both in real games and bot games. When it is in effect, it seems to not work on either heroes or creeps.

I know this is somewhat vague to go on, so I guess my question is what the best way to try to reproduce the issue would be?