Need help with my screen recorder (hopefully easier to understand.)

My screen recorder - Elgato HD60s is slow and keeps freezing when I try to edit it in an outside movie editor, such as Sony Vegas.

Is there a way to stop it from lagging, or do I have to edit it within the program that come with the HD60s (I don't want to do this, but do I have to.)

If this question makes no sense, please say - and I will try to explain better.

EDIT: Sorry for the double post, I thought I'd be able to delete the other (if I can, I can't see it.)