I tried searching and didn't find this issue, so I hope I am not repeating it.
don't know if its a bug or what but has the HDR shooting speed changed?
I am using a 550d with the version from May 9th 2012 before this version when I shot a 5 exp HDR the shooting would be continuous like 0-2-1+1+2 but now when I set it up for 5 shots it goes 0 (pause) -2-1 (pause) +1+2 for a moment I thought it was my SD card, but tried the older version and it worked as I want it (no pauses between shots) also if I set the native AEB in the camera this will shoot it continuous, so it has to be something with ML.
also on this same version, the EXP-SIM when on live view acts weird, I was on a setting that required 1/20 for a proper exposure, but if I set it up to live view, the exposure "indicator" would not move from -1 no matter how much time I set it to, if I exit live view then the exposure indicator works correctly.
hope I explained myself.