Sony Vegas rendering black screens in video?

I had this problem. It was normally when I would speed up a clip or slow it down. (or if vegas just hated my clip for no reason) what i found worked a lot of the time was if I right clicked a clip and went down to switches and clicked disable resamle (it might be forced try both) it worked good... eventually i just updated my vegas and the problem disapeared. (by update i mean went from Pro 8 to pro 9)