Previous to this happening had you topped up the pressure on the boiler??. I had the same problem and found that the tap on the filler loop had been left in the on position. An easy way to check is to drop the pessure below your desired mark, then wait to see if the pressure comes back up on its own, if it does the tap could be in the on position turn it the oter way and see what happens
diver, January 2009
