Had similar problem myself with K11. I suggest that you also examine the electrical connectors that connect to the bulb units, as they will probably have overheated. This is due to a poor connection with bulb(s). If this is the case replacements (from breakers) can be bought online for approx £3-4 each. Then replace both bulbs for new, and clean contacts on replacement electrical connectors with emery cloth. This should solve problem.
Smudge of the North, October 2009
