You need the following completed in Astaro to get Xbox Live working correctly:
1. A static IP address for the Xbox
2. two packet filter rules to allow the two different ports.
xbox--> Xbox1(3074)-->Any
(source) (service) (Dest)
Xbox--> Xbox2(88)-->Any
(source) (Service) (Dest)
3. Nat rules setup(DNAT/SNAT)
Traffic Source: Any
Traffic Service: Xbox Live 1
Traffic Destination:External (WAN) (Address)
NAT mode

NAT (Destination)
Destination: Internal (Address)
Destination Service:Xbox Live 1
Automatic packet filter rule:YES
-------------------------------------------
Traffic Source:Any
Traffic Service:Xbox Live 2
Traffic Destination: External (WAN) (Address)
NAT mode: DNAT (Destination)
Destination:Internal (Address)
Destination Service:Xbox Live 2
Automatic packet filter rule:YES
This should take care of all your issues related to Xbox live not working, please ask away if you have any questions.