in the attached file, press 1 twice, then 2 twice, then 3 twice , then 4 twice.
Now quit the game and press first 2 (twice), then 1, ...
The result is different. Basically it seems the BGE is "caching" some information from the previous action, and re-playing.
I tried changing the animation layer of each action actuator, but with no success.
bug in 2.66