The nature of the platform is the problem. Somebody like Steve Gibson or other master of machine language needs to write a great MIDI application for the PC using machine code only.
In the meantime, try using a stadard First In First Out IDE Controller instead of a Buss Master. You want the fifo because that is exactly how the MIDI transmission is ocurring, thus eliminating other data to slip in and putting the other data aside, causing a data break (or what you call a glitch)in the transmission of the serial data.
To me, both PC's and Macs are essentials musically. Next time however, instead of buying more PC componentry, and if you want to eliminate this headache once and for all, go with a Mac. Yes, it, and its software costs more money, but most music applications do a lot more too. For instance, you can make changes on-the-fly, realtime with just about anything. Even drastic changes can be made. With the PC versions you usually cannot. Mac MIDI software is so fine tuned these days, that you can manipulate in realtime at any level. Oh and of course it's all free of data breakages. You can even daisy chain keyboards together these days (something that was once a taboo practice and asking for problems)and at the worst, maybe squeeze a milliseciond of latency out of the system using a Mac.
PC's defineately still have their place and time. They are far better in post production at tasks like wav editing. These days using 3+ GHz machines, I can usually batch an entire long noise reduction multi-process with a PC and complete an entire job in the same time it would take a Mac for the first cut and paste of the same multi-process (although it never used to be that way). Searches in a sound library are faster with PC's too, as more search handles are enabled than Mac, and so with more handles, much more of the processor chip is utilized while searching.