Green screens on film when comes out of compressor

Hi guys

When my film comes out of the compression stage I keep getting random green screens instead of a clip, audio is still ok. Definitely wasnt on my time line. Please can any one help. I am using an Imac with a 4tb G-Tech drive attached. Help please.

Im using Final Cut Pro 7 and Magic Bullet Effects. The radomness of it and the fact its not on the time line is baffling. I also rendered the affected clips seperately to see if that changed them to green on the time line, but they were still viewable.

Any ideas?