...I'm running the Steam version on Win7.
Have a look in our
General Machinarium topics board and try some of the Windows 7 specific suggestions. ( they just might work for you too )
I've tried reloading from a couple of different saves and playing back to this point. The same thing happens.
Have you tried re-downloading the game itself? ( several folks that posted here saying they were stuck somewhere in the game solved their problems by re-downloading the game )