I don't know about this make of boiler but I've tried the following with mine and it worked...
Try switching it all off for 5mins then relight the boiler (holding down the ignition button for a few seconds).
Failing that, check to see that the boiler pressure has not dropped too low. It should be between 1 and 2 bar (I keep mine at about 1.2 bar).
If it is too low try increasing the pressure by turning the (black) tap a little and let some water into the system. watch the pressure guage carefully and turn tap off quickly once at 1.2-1.3 bar.
Best of luck.
Elodie
December 2009