Excellent, thanks Greg. That's all it was, there were two functions with _P - and removing the _P did the trick. For what its worth I'm working on a project similar to your SHT15 temperature and humidity monitoring system. The Arduino in my case has a LCD and has the intelligence to function as a 4 channel 7 day timer. The end goal is to be able to program it and override channels for specific periods of time remotely. Think a heating / hot water controller with extra functionality and your there! I've got the 7 day stuff, the temperature sensing (with a LM35 sensor) and the LCD working. Now I have the connectivity working I can put the two together. I think the Arduino will post to a website temperature readings on a fixed schedule. If there are any override conditions set or a change in program the webpage response can include these.
When I have a semi working prototype I'll post more details.
Thanks again for your help, I've been stuck on this for a while!
Richard