Hi,
See if this is your problem:
(taken from the FAQ)
However there is a known problem when using a dual display mode. If setting the second monitor as the primary monitor in Windows, DeskTask window cannot be moved. The only workaround is either setting the first monitor as the main monitor or, if using a Nvidia Card, configure the monitors setup in the Nvidia Driver options.
If it is there is no workaround at the moment for that specific configuration.
Thanks,
André Santos Carthago Software Support
http://www.carthagosoft.net