Cold Radiators

[nevillioni]

Cold Radiators

Hi,
I've got a Combi Boiler and a wierd problem.
Untill about 2 weeks ago everything was working fine.
But now only one radiator downstairs is getting hot, the others don't even get luke warm.
The one radiator that works is in the kitchen and is red hot, also all the radiators upstairs get really hot.
I've tried bleeding the radiators by starting at the furthest radiator from the boiler
( the boiler is in the kitchen) but only got a little bit of air out of one radiator all the rest squirted water straight out.
After bleeding I've re pressurised the boiler so the guage is in the Green.
If i turn the boiler off and re-boot it everything works fine...all the downstairs rads get hot but after half an hour only one downstairs radiator stays hot ?

Any ideas whats going on ????

Cheers