I am seeing the very same effect and it starts driving me nuts!!!
My host is running Windows 8 and the guest Windows Server 2008. After dis- and re-enabling of the network adapter the connection is up for a few minutes (just enough to start a VPN on the guest) and shortly after the connection drops. It's essentially become unusable. This used to work until workstation 9.0.1, I would claim, but since 9.0.2 it's a nightmare!
I am using DHCP (i.e. automatic IP address and DNS server address resolution). But since Windows' "error wizard" reported that the DNS server is not reachable I also tried to specify the DNS server's address manually, but that didn't change or help anything! I also disabled IP v6, since in some other forum I read, that this may cause problems, but again - no difference!
Of course the host's network connection is running stable!
Any ideas, anybody?