1080p vs 1080i

I had a problem recently with the HD channel sound being out of sync, especially BBC1. Tried every setting I could think of on both box and TV to fix it, with no avail.

Then remembered that the box had recently spuriously reset itself, and that my problem had probably co-incided with that. As a result, I hadn't realised that the v-format was set at 1080p. Changing it to 1080i solved the problem!

Anyone else noticed this, or have an explanation as to why? I've looked around but can't find a description of what the full difference is between the two.

Black Hole

May contain traces of nut
I think you will find that changing the VFORMAT caused the re-sync, not any specific change, and returning to 1080p will remain in sync.

I observe this on a regular basis, but have never found an explanation why it happens. When it does, a quick tour of the VFORMAT button (causing the HDMI to renegotiate) sets it right.