well unfortunately time did tell me that I haven't gotten it right just yet
After running the dpc tool overnight, at some point during the night a small spike occurred, the spikes occur very infrequently now (maybe once every 6-8 hours) so I'm not sure if those are the cause of the issue - can't hurt to get rid of either way though. The lagging is still occurring - roughly once every 4 or 5 motion recordings. They are still about 4-5 seconds long and there usually is NOT a latency spike accompanied with the lag in the clip.
The whole thing is rather inconsistent and very tricky to pinpoint - I thought it was resolved because I had no bad clips for many hours and then the problem slowly came back - may have to email Ken and see if he has any suggestions...
If you have the dpc spikes only happening every 6-8 hours and they don't correspond to the lagging I would say that the dpc issue is not causing your BI problem. It is a good idea to have a clean dpc check, however, it is normal to have a dpc spike at certain times, like your computer is doing a backup, disk defrag, update checks... The windows event viewer may help you peg it, try creating a custom view for time period(s) that the spikes occur, it may give you a direction to go. You are right, dpc problems are difficult to peg and tricky.
Since the problem of lagging is occuring on all your camers and it only occurs using BI (you stated it is fine thru the web interface) I would concentrate on the disk activity and BI settings. For the disk activity check you will need to create a custom view (set for the time the lagging occured) in the windows event viewer, and run windows resource monitor or performance monitor. Resource Monitor is real time, you would need to be viewing it at the time it occured, Performance Monitor will let you create a custom data set that you can review at a specific time. There is a great deal of help on the internet on how to create a custom data set for PM, it is a complicated program but is excellent in pegging system issues. It may be you have a sector on your hard drive that is starting to fail - this can causes lagging in realtime recording because the computer/hd uses error correction to "fix" the issue - but it takes time and can briefly freeze the OS and/or programs, this was actually a problem for me at one time (and it was VERY hard to peg). It may also be something as simple as a BI setting, you may want to install the software that came with your cameras and see if it can record without pausing, if it can I'd be looking at BI, if not I'd be looking into the system.
Keep us apprised of your progress, sorry for the pain in the arse this is. On the good side when this is done you will be FAR more knowledgeable on computers and cameras.