Players with slow CPU's managed to activate a creature skill, play a card and use the "cancel" button in a rapid sequence to re-use cards in an infinite loop.
In 1.25, after using a creature skill, a 1/10 of a second pause is added (same as the one used for playing a new card). It is the time required for the script to complete its function, during that time a new command (another creature skill, card, etc.) can not be used.
P.S. : this is also the reason why creature's skills do not have a "real" cancel option; giving back the cost of the skill would create a huge array of fast click combos and it would force me to make the UI much less fluid to keep control of all the possible exploits.
It is not because, as commonly believed, I am punishing the player for a bad choice. I said something similar once in the flash forum, but I was joking, and someone mistakenly left his sarcasm detector in the microwave while nuking a smurfberry pop tart.