Bug: Skill lock

Happened to me all the time, I'm THM, setting Sac II at slot 21, and Macro it. Many time when I press the macro for Sac II right when the current spell about to finish (all thanks the stupid idea of we can not queue action anymore) the spell will be lock (gray out). /recast will tell it's ready, but you cant activate it. The only way to make it active again is to cast another spell. Needless to say this bug killed me and my pt many time. So far only happened with Sac II, the Cure II next to it (slot 22) seem to work just fine.