We had some issues using high-res displays (3000x2000 etc) with Diptrace 3.0.0.2. For example, the menu icon spacing was off which caused them all to be basically useless - so we turned them all off (press Ctrl-1,2 etc.)
However we came across a solution and just wanted to share - install the 32-bit version of Diptrace.
Silly but it works.