Steve,
As Anumod has mentioned, you'll want to make sure you have 2 network adapters assigned (1 mgmt and 1 sniffing). It sounds like maybe you tried to assign the same interface for mgmt and sniffing.
Be careful with configuring the management adapter to Bridged mode, as the VM will obtain an IP address and remain and act as if on the same network segment as your host machine. If you do this, you will want to make sure there is strict enforcement of firewall rules, etc.
Thanks,
Wes