Yes & No.
The Cube may be connected to two separate networks at the same time if they use different network address ranges. As an example, the following is allowed:
Cube wired connection: Linksys router with an address range of 192.168.1.1 / 255.255.255.0
Cube wireless connection: Airport Extreme router with an address range of 10.0.0.1 / 255.255.255.0
Wired and wireless connections to the same network, or using the same network address range are not supported.