I have installed OS X Mountain Lion as a VM in VMware Fusion (version 4.1.2) for environment testing. The host OS is OS X 10.7.4, and is connected to the internet via a wired connection (in fact I get the same problem if it is connected via wireless as well).
As long as VMware Fusion is running, my internet for the Host OS stops working, but remains functional inside the VM.
I am using NAT for VMware Fusion.
For additional testing, I have an Ubuntu box on Virtual Box. When VMware Fusion is off, I have internet on both my host OS and the Ubuntu VM, and when VMware fusion is running, I have no internet connection except inside VMware Fusion.
VMware Fusion blocks internet even if the actual VM is suspended.
Best Answer
You have likely set your VM to use the same IP address as your host machine. This article talks about it. If both are using the same address, any traffic destined to the IP address of the network adapter used by the host OS will be passed to the VM.
Simplest solution is to ensure everyone has their own IP address (the Host machine has one, and the VM has one that is on the same network).
This article walks you through reconfiguring the virtual network adapter. The part you need is quoted here:
Item 6 is likely to be what you need to focus on. Remember to make sure the IP address for the VM isn't in use elsewhere in the network.