David,
You're asking a really good question here. I hope it gets some attention, or at least a response, from the developers. This is the reason that I have never used Max for realtime performance.
I do live video improvisation. At any point in the performance, I need the capability of loading several short quicktime loops into a patch from a large database of loops on hard disk.
I have never been able to do this in Max without the interruptions you describe. I've upgraded computers several times, moved from slower hard disks to faster ones, and eventually installed the fastest ssd's available, and still no luck. As you did, I spent a lot of time trying to find the file size and codec. Again, no luck.
Some of the VJ software in current use has the same issues. I see some problems at times with Resolume, VDMX and Modul8, but their performance is much better than Max6.
I hope someone knows a good solution for this. It's a serious limitation that doesn't appear to have a good workaround. It if could be solved by Cycling74, Max would have a real advantage over many other video app's. Right now, it does not measure up well at all.
Best regards,
Michael