Need help with Boot Magic!

Hi, I've got a project machine that I'm working on to have a multiboot setup with Windows XP/98SE, DOS 6.21, and eventually Linux. I've got all 3 microsoft OSs installed on 3 different partitions using Partition Magic 8.0 and Boot Magic 7.0 (I think that's the version?). In any case, the boot menu shows up on every reboot/power on, and I can select any of the menu options, however it can take anywhere from 2-10+ boots for the OS to actually load in any of their cases. When the OS doesn't load the screen either hangs on black or on the "Loading BootMagic" text screen that pops up before the graphic interface loads. Rebooting and reselecting the OS I want time after time seems to eventually make things work, but this is sort of annoying and I'd like to find a way to just have them load the first time. The only possible clue I've had is that with all the OSs at one point or another I've gotten an error about accessing line a20, which I've looked into and addressed by adding the /M:2 flag to my HIMEM.SYS line in CONFIG.SYS. This has solved the problem once I get the OS to load, but it seems as though the system hangs before it even begins loading the OS, hence making the change in CONFIG.SYS not likely to make a difference. Furthermore, when the system hangs, I lose the ability to turn caps or num lock on and off. I should probably mention that I'm using an Iogear USB KVM with an Apple USB keyboard and Kensington USB wheel mouse to control the machine (I run a Mac usually, but wanted a project PC). In any case, sometimes popping a PS/2 keyboard in directly seems to fix it, but it may just be coincidence, as sometimes it doesn't work at all. Anyways, any help would be GREATLY appreciated! Thanks!