video

Im working on a translating voice over project. 

the video reference with the audio track im translating freezes and goes black, audio keeps playing but nothing shows on video panel. 

i need to see the video to make sure i am doing the voice over properly. any ideas as to why it happens?

it will start playing good and about half way through it stops. 

i listen to the audio only to do voice over but at times it wont match the video. 

for example they pointed to the camara to talk to audience i didnt know and it was way out of sync.