How many instances are you using though?
I mean, how many sounds are you trying to play at once, or seperately, a lot of devices have a limit of 32 channels, like the iPad2 - so it might just be a limit behind the scenes, that is affecting the sound hardware on that particular PC. Maybe that one PC is a little older, with a slightly older sound card that has less channels available.
Sound effects should be fine at 11khz, not that it's ideal quality - but up-rating a sound file from 11khz to 22 or 44khz, well it's pointless unless the software is doing some seriously miraculous filtering. You are really just doubling or quadrupling the file size for the same sound quality. What might be worth looking into is whether or not the sounds are stereo, as they would take more processor power and memory. Any sounds that can be mono, should be mono.
I wish AppGameKit had just a few more commands for sounds, it's depressingly similar to DBPro in that regard.
I am the one who knocks...
