Sony Vegas Video Overlay problem?

Computer specs: Windows 7 Home premium 64 bit Intel Core i7 OC @ 4.5ghz 32 gb ram GeForce GTX 780 3GB Graphics card H80I CPU COOLER 850W power supply 2x Samsung SSD 256gb each ASUS X79-Delux motherboard I just got this computer and sony vegas pro 12 keeps crashing everytime I bring in 2 videos in the same screen at the same time. It crashes on other things as well, but this is the most important one that I need to edit my videos. Basically it renders out fine normally, but there is a scene where I drag 2 videos on the same screen and shrink both of them to fit in the screens width it becomes super laggy and if I watch it for over 2 seconds on the preview window it crashes. IT also doesnt render and freezes at that exact spot. There was a setting that I changed last time this happneed a few years ago but I cant remember and I googled everywhere! .