Excellent job turning on the AcquireSupport popups, you saved us the time needed to re-test and get that stopping point. Bravo!!

This is strange. It is getting into code that is not supposed to be reached when taking bias frames. In case you're interested:

    Do While CamStat = 3 Or CamStat = 12                        ' While exposing Light or Dark (not Bias, div by zero!)
        c_exposureRemain = CInt(ActInterval - (CDbl(Now - StartTime) * 86400.0))
        c_exposureProgress = (ActInterval - c_exposureRemain) / ActInterval
        If PtgPrefs.Simulate And c_simImageTimeCompress Then
            Timeout = Timeout - 10                              ' 10x rate for simulation
            Timeout = Timeout - 1
        End If
The highlighted line is where it's failing. Division by zero. There's no sense waiting on a bias anyway. But it saw the camera return a status of either 3 or 12 which is not right:

MaxIm Scripting Help for CCDCamera.CameraStatus:

So at this point the camera is not returning an accurate CameraStatus, and as you have found, it is intermittent. Unfortunately this will need to go to Diffraction. But I would strongly suggest you update the camera driver and or MaxIm. Or maybe you did that already and that's when this "just started happening"? In any case, I can't help you on this sorry to say (other than to analyze and describe the exact error that is occurring). If you need help with Diffraction say so, I sometimes get on their support forum in support of ACP customers.