Q: Software updates, Itunes store and App store, do not work

I have a macbook Pro using Mountain lion 10.7.5. Itunes store, Software updates and App Store all fail to connect. Itunes tells me to check my connection.

When I attempt to access any of these on my G4 ( still running Snow Leopard 10.6.8)  using the same network all is fine. ( I have copied the network info as well as access, security, sharing...

I have never had success with updates on the macpro  but then I only got a serial number for it today. ( It is 18 months old and the  store forgot  to assign it when I had it repaired  5 days after purchase.)

I think I have tried EVERYTHING. Date in settings etc.  I have followed all teh how to sites for ITunes store. I really need to update this. I would install Maverick but it is only available on APPs store which also does not conect. 

HELP 

  RR Perth