THE best way to suss this out is for you to upload and share your project, which can be done privately. Then someone can run it just as you see it.
What version of VP is being used? What are your PC's specs: CPU/GPU/RAM/free space on C:? Mention specific times where these errors occur, if possible.
Here's how... http://nch.invisionzone.com/topic/23659-tips-for-getting-help-on-this-forum/
If it contains sensitive material link it in a personal message (PM). Click the envelope above. It won't be passed on or retained.
Use FILE|SAVE PORTABLE PROJECT AS, not simply SAVE PROJECT, and don't forget to share it.