I am having the same problem. It is EXTREMELY FRUSTRATING and annoying.
Could you please provide a checklist to check for compatibility. Win7, Firefox or IE (both have same problem).
I tried shutting all apps, killing browers, flushing cache and cookies, but it keeps happening.
recently i noticed that sometimes when i make a move on tactics trainer it shows my move on the screen but doesnt do my opponets move or say i solved the puzzle
please help this problem started after the update on live chess