Menu thumbnails are too big

[HMD]

Please advise me.
When I create a manu in Pinnacle studio 12 or 14 the thumbnails look alright in the project, but when they are viewed either directly in Pinnacle studio or on a DVD, the images in the thumbnails have 'grown'. They are much too big.
Also, often it happens that a menu thumbnail - which was ok before suddenlig are half covered by a gey area, thus only showing the top half of the thumbnail. It seems to have a life of its own. It does seem to be very stable.
How do I create a decent menu with out these problems?