Vaillant Ecotec plus; no hot water?

I feel that perhaps I have caused the problem with my boiler.
I am intermittantly having problems and recently thought it may be wise to turn the boiler off while we were away for a weekend. When we returned the radiators would not heat up. I fiddled around with the taps underneath, bled a radiator ( as I had increased the water pressure) and then everything was fine. After a week the hot water is now not coming on. However, the tap symbol is showing.
Tech dept at Vaillant say it is the diverter valve. Could I have unprogrammed it, messing about with buttons and taps? I seem to be trying to work out its problems since it was installed two years ago.

Catherine
April 2009