I have had a vaguely similar problem with guest networking directly after updating to Fusion 2.0.3 from 2.0.2. My setup is thus:
Host: MacOSX 10.4.11
Guest: WinXP SP3
After the 2.0.3 update, the guest failed to get a network connection via "Bridged". My Mac is in an environment where it connects to the network via WiFi, but I use an ethernet cable instead for speed and robustness (and I have never gotten the bridged connection to work over my workplace's WiFi, though at home it works fine). I have my Mac network settings configured to prefer the cable when available. Anyway, it is in this context that I had successfully run guests in VMWare prior to 2.0.3.
After network connections failed in 2.0.3, I had success getting the guest to connect if I turned off the Airport. Note, that, in theory, this should have had no effect since it should have been using the ethernet connection, but it did. The guest started to operate with the Airport off, but the host (Mac) networking then failed. After see this, I decided that there is definitely something wrong with the 2.0.3 update, and I uninstalled it and re-installed 2.0.2 (also remembering to uninstall and re-install VMWare Tools). This now seems to have put things back to the functioning I had had prior to 2.0.3.
You may find a solution somewhere in this tale. Perhaps you, too, have a double network connection, which seems to be at the heart of this problem with 2.0.3. Maybe, though, you can get functioning without resorting to 2.0.2. As I said, I was able to get the guest working in 2.0.3, though for me, it came with the unacceptable sacrifice of host network connectivity.
