This printer the HP 1020 worked with my VM while using Tiger. Sometimes I had problems getting it connected. But I could always resolve it someway. Now that I have Leopard I can't get it to work at all. I'll have to boot Tiger up from my external, and run the VM there just so I can print checks (MICR) with the 1020. This has got to a be a problem with Fusion and Leopard. Don't think Vista has anything to do with (I've been using the Vista driver for the 1020 since it was made available this summer)
Ping the Host (OSX) through Guest (Vista)
Have no idea what that means, but just so you know, the HP 1020 isn't compatible with the Mac. I did delete the printer in Vista's Print Window, and then tried to reinstall it, and during install, it doesn't see any new printers... so I guess the 1020 is being recognized as an already installed printer... ? Oh, did I mention that I spent four hours trying and failing to move the 1020 from Offline to Ready in Vista? Before, with Tiger it only took twenty minutes. And I thought 20 minutes was an ordeal.
I had a similar issue with a HP color laser printer that wasn't compatible with OSX, only with XP. I got so sick of it I sold it again.
What happens when you plug in/turn on the printer while the VM has focus? Do you see that yellow balloon in the bottom right corner in Vista?
When you open control panel/printers, do you see anything happening/installing?
When you open OSX system preferences and look under Printers, do you see something installed?
Do you have the option of trying bootcamp? If so, please check to see if the printer is working properly natively.
Last but not least, check the console logs of OSX and look for USB errors. You wouldn't be the first on Leopard.
I havent seen it mentioned here so I will ask. Have you installed and configured Apples Bonjour for Windows? It will find your printers and configure them for you. A little inside info if you havent already done so. When setting it up, always use the generic driver, not the manufgacturers driver. Try this if you havent already and I am sure it will work for you. You can download it for free from www.apple.com/downloads