As a test, under OPTIONS|EDITING tab, toggle the Use Hardware Acceleration check box to the other state to see if that makes a difference. Clear Unused Cache Files, under OPTIONS|DISK tab.
What version of Videopad is being used? Share the project and mention specifics of where the issue occurs. Someone will check it out. It's not difficult...
Here's how... http://nch.invisionzone.com/topic/23659-tips-for-getting-help-on-this-forum/
If it contains sensitive material you can link it in a personal message (PM) to me, via the envelope above. Be sure to FILE|SAVE PORTABLE PROJECT AS, not simply SAVE PROJECT, and don't forget to share it.