Did you start play from a recording file, either in Standard or Theatre view as required, or did you start it from the Guide or start playing the channel itself, either from the Television section of Standard View, or using the "Live TV" button, or channel numbers on the remote?
If you do start playing a recording and it doesn't start from the beginning, try pressing stop twice, which is how a Bookmark can be cleared, and then play the recording file. Does that then start from the beginning?