Help with Worcester greenstar ri?

Hi, drained a central heating vented system today to fit a new rad valve, turned the cold water back on and restarted system, boiler tripped (Worcester greenstar ri) sounded really rough as though there was air in, tried to bleed radiators but no water, checked cold supply and tank was full but would not drain, suspected blockage in cold feed, used hose pipe to push water back through system until water came out in breather above tank, then blocked this and water then came up cold feed into tank so clearing blockage, managed to bleed radiators ok but now can't get boiler to stay on, keeps cutting out after approx 1 min of running. Think i have done some damage to the boiler, Can anyone help?

Gary
October 2011