Turn it on. Wait until it is started up.
Hold the power button for 20 seconds until you hear the drum noise. It'll do a soft reset and you won't lose anything stored on it.
What model?
Xl live IQ, have done soft reset, also hard reset, still the same.
Have sent email to TomTom, after reading up on error 148, it seems to be mobile phone network issue (Vodafone) as that is the network TomTom use.
I will wait until I get reply from TomTom, and see what they say, it seems to be affecting other contries as well, if it's anything like the last time it happened, TomTom will extend customers live services by 3 months as compensation.