bad hamstring ache

pots
pots Posts: 109
i have a problem with my hamstrings aching,not tight,anything over 1 1/2 hrs they ache quite bad.this has been happening for a few years and with medical help nothing has helped to cure this. I have had scans on my back and physiotherapy privately, i have had massages, acupunture, sports physio. Bike set up is ok, checked by an ex-pro and i stretch regularly.
Then last spring ('06) my employer hired in a physio company to better the work force and help with any aches and pains we had. Having explained my situation, i went on a machine that was linked to a computer. It was like a leg ext, leg curl machine that moved, but i had to push (or pull) against it. The readings showed i had weak hamstrings, so we progressed to strengthen them. This was seemed to be working and then the employer withdrew the service. So i joined a gym in January and carried on with what i was doing with the physio twice a week doing hamstring curls and leg press working up to:
leg curl - 3 x 10 @ 40kg
leg press - 3 x 10 @ 45kg
So since January i have built up my miles slowly, up until last week when i did a thirty mile ride and bingo, my hamstrings hurt again. I should say that i am 52 and my diet is ok, i am 12 stone. The weight training doesnt seem to have made any definition on my upper legs, but my calves are well developed. I think i could ride for a very long time if it wasnt for my hamstrings, i dont have a problem with my quads of calves.
Does anybody have any suggestions please, to what i could do? As you can see i have tried almost everything.
Anyway i am going to have a cup of tea now as it has taken me over an hour to type this.
Thanks