I haven't seen this problem brought up so far. I have a number of ALAC files that I made myself from vinyl or 78 rpm originals, all at 48 kHz sampling rate. They all play perfectly well through QuickTime, but in MC certain files will turn into rapid-fire machine gun sounds.
Using MC to convert those files to FLAC retains the machine-gun problem, but converting those files to FLAC outside of MC, then importing them into MC, results in a properly behaved audio file.
I have not found this problem to occur with any other but these particular files -- i.e., I made them myself, they're 48 kHz and 24 bit. Yet the situation isn't consistent: certain files will have no problems, and other ones do.
I have placed a copy of one of the offending files here:
http://scottfoglesong.com/ch_ora.m4aso y'all can check this and find out what's going on, if possible.