Some time ago, I captured video from High tape through FireWire connection to Sony Vegas. I don't recall the version exactly but I do know that when this capture completed, I was able to see the video properly. Now, when I play the video, the first few seconds of it play fine and then it displays this gray matrix with rows of dots. I will attempt to upload an attachment of this matrix. The computer that is playing the video has been reimaged several times so perhaps something was not reinstalled on it after the reimage. Could it be missing a codec of some kind? Thank you in advance for any guidance you may have.

It sounds like you are missing a driver. You might consider downloading the freeware program VLC Media player (https://www.videolan.org/) then play the video with VLC media player. Then you can hunt for the missing driver. If it does not play perhaps the video file is corrupt????

Sidd