Nigel,
I'd agree with Redroger - breakthroughs seldom come immediately, often come suddenly, and usually come unexpectedly.
Case in point: I'd been vainly trying to track down a wedding in Tipperary for months. I Googled some of the information I had (as I'd done many, many times before - one of my mantras is "check, double-check, triple-check..."). After looking through several pages of results, I eventually found one I didn't recognise that looked interesting. It turned out to be a 6 year old post on another genealogy website's message board. Obviously I joined up, posted a reply, and waited (with little hope, assuming that whoever it was had given up).
I was delighted to get a message a few months later - it turned out to be a cousin of my mother's. We shared (and double-checked) each other's information. We now continue to research independently, often comparing notes.
Remember that your RootsChat postings will show up on Google/MSN searches, and people not on Rootschat may find them months/years down the line. So never give up!
Pete