I'm using the demo version on vitual PC 5 ???
I'm following the "BOX" tutorial and I'm placing markers. Unfortunately, I don't see any calibration going on. I have 10 markers, but they are all grey even if I click the F9 key

we did not make tests in Virtual PC but we suspect that there could be problems when we draw the 3D.
Anyway, the calibration should start.
Is the Progressive calibration enabled in the preferences ?
what happens if you click on Camera - Calibrate (maybe that there is a problem with the F9 key in virtual PC) ?