I'm actually posting this on behalf of my dad's BI setup. He'll probably chime in here. The attached screen shot is of his system and is of the LIVE console view. I've drawn a red box around the system clock (very top left corner) and the enlarged time-overlay on one of the cameras (first top left camera).
To answer your question, yes, the system OS clock is running SLOWER than the BI time stamp. The clock in the top left corner mirrors the OS time (in the task tray bottom right corner). The overlay on each camera is put there by BI, not the cameras themselves. All of the cameras use the same overlay template in BI, and all the time values are synced perfectly between the cameras. It's just that they run a minute faster than the OS.
It makes no sense, as I can't seem to find any option in BI that would allow BI to pull time from anything - so I assume it gets its time code from the OS.
All of my own BI servers (I have four of them running at various locations) are synced to the second between the BI overlay and each PC's OS time.
Just so it is more clear, you are saying that the Windows OS clock in the bottom right of the task bar is running a full 1 minute 15 seconds slower than the time being displayed in your live view within BI that you setup in BI as overlays? Or are the times in your camera views being displayed from each camera independant of BI (meaning you set them up from the camera web interface)?