1013532, on Apr 10 2011, 05:52 AM, said:
When opening the App Store and attempting to Sign In through the Store menu, the system responds with the message "No GUID is available. Contact Support for assistance." in red font.
This seems to be a network problem. I had to networks cards installed, one on board and the second one as a pci card.
The onboard network controller was assigned on en1, the pci card on en0. In fact I used the onboard controller on en1 as it support a 1000baseT connection. To solve this I
1. Plugged of the pci network card
3. I deleted the interfaces in System Preferences
4. I deleted NetworkInterfaces.plist in /System/Preferences/SystemConfiguration
6. Add the onboard controller as en0
7. Voilà: AppStore works
As I don't need the pci network controller (was for mere installation necessities as the onboard controller needs special kext driver) I didn't reinstall the card but I guess it's save to do it as it would be configured on en1 now.