Finding shorts in boards

I've got a board here with a short between ground and the +5V rail (actually not quite dead - I'm getting around 10 ohms between the rails) Any useful tips for finding the fault? It's a large board, multi-layer, lots of silicon on it unfortunately :-( Are there any particular components that are likely to fail in this way that might be found across PSU rails? (decoupling caps, certain ICs, crystal modules etc.?) Given a suitably sensitive meter is it sensible to assume I can try and home in on the short location a little? (I've found readings between GND/supply on various LS chips of anything between 9.5 and 12 ohms so far) I've checked the board for particles of anything that might be causing the problem, plus I'm halfway through ruling out any of the socketed ICs. Of course if it's a problem with the multi-layer PCB itself... eek! (do these ever fail in such a way though? It's a commercial board which used to be fine) cheers Jules