No volume control- headphones or dock

I can't control the volume output of my 1st gen Touch on firmware 3.3.1.

When I plug headphones in the volume slider doesn't appear, reading around I see this was a pretty common issue when people updated to 3.x so I ran a jailbreak and installed SBSettings and the volume slider widget - it doesn't control the volume, still stays at a constant level.

I plugged into the dock and have the same issue - no control over volume from the iPod.

So although I was initially thinking a headphone jack might need replaced I'm not so sure now that when docked it still has the same issue!

Any ideas?