I had a new gloworm micron fitted in december 2004.
Everythings ok until I turn one or any radiators down with the TRV.
When I do this the boiler light goes to "reset".
If I leave the rads running about no.3 or above, everythings fine.
Check thermostat, it may be that the boiler is over-heating, when the rad valves are open fully the heat will be transferred to the rooms via the radiators, if the valves are closed it may be that the boiler stat is not cutting off when it reaches temperature.