I use my Blackberry 7800 for projects that require GPS, such as weather balloons etc ...

but it seems O2 may have deactivated my sim?

On the home screen I get the message: "Sim not provisioned: 2"

and in Settings > Advanced Options > Sim Card > MEPD

I get:

What do you think?

Many Thanks

Sure looks like it. With most pre-paid SIMs the money/minutes expire if you don't add more periodically.