Drayton LP522 behaving strange :-)

[nicejumper]

Ok, just so you know, I do not have any plumbing experience but I am able to identify the key items in the plumbing system.

I have the following setup:

• Potterton Netaheat Profile boiler
• Drayton LP522 programmer for hot water
• Honeywell wireless programmer/themostat for central heating
• A cupboard with a hot water storage tank
• Tanks in the loft for hot water and central heating

There may be a specific name for this setup, who knows !

The central heating system works fine but the issue I have is when I have the hot water turn on. I have set the Drayton timer to come on at regular intervals. This works fine for 99% of the time. However, 3 times in the last couple of years, the programmer appears to get 'stuck' just after midnight! This 'lock up' of the system has the following behaviour:

• The central heating is on despite the Honeywell programmer/themostat not indicating for the central heating to be on
• The pump is pumping
• The boiler is heating
• The Drayton has both central heating and hot water red lights on.
• None of the buttons on the Drayton respond to user input.

I first thought is that this is a fault with the Drayton programmer but would like the opinion of experts. Does anyone have any ideas on confirming the fault in the system? It would be a pity to buy a new programmer only for the same fault to appear.

Thanks in advance