Many times on different programs i have had one clip that will not work. I have to open it in another program and render it out then add it back in. I have been using Vegas 9 with an i7 and gigabyte board, windows 7 64 bit and no problems ever. the bad clips i used to encounter were in premier. Also if they are HDV clips, I changed my ram buffer to 100% in capture properties when i am capturing.