Renault Laguna Estate Problems?

Hi,

I recently bought a 01 renault laguna estate (supersport 1.6 model). However I am having some problems which I hope someone might be able to help me with.

Firstly the tyre sensors keep flashing indicating a problem with one or sometimes two of the tyres. I have checked the tyre pressure several times and it has be correct but still the lights keep flashing. Any ideas??

Secondly the the service light is illuminated on the dashboard even though it has just recently been serviced. Can you me some advice on how to turn this off as it's driving me nuts!!

Thanks!