Now that we have all had a dig at Andrews microshite,
No offence intended Andrew, we like to have a laugh and I think I can speak for the rest of the guy's who have added, that you deserve an answer for your pains.
Firstly check your PIRs batteries and your door contacts are fitted correctly ( gap ),
ensure tamper switches on control panel and outside sounder are fully depressed,
If anti jamming is enabled and you are in an area of high radio interference, then try turning off anti jamming(available in options).
That's all I can add here.
e manno, July 2012