I worked out the solution, so I thought I would post this here to help anyone else who stumbled upon this thread in search of this answer.
To be clear, when I found this solution my system was up to date with OS X 10.6.5. Vista 64 Service Pack 2, fully updated. Bootcamp drivers 3.1.
You may need to be upgraded sufficiently, equally so you may just need the bootcamp drivers from your OS X disc installed.
My system is a 2010 Mac Pro 3.2 Quad.
I shall try to give the below instructions in the best English I can, I am translating it from a Dutch version of Vista so the buttons I instruct you to click might be worded slightly differently in the English version.
1. Open System Configuration
2. Open Device Manager
3. Find and open "Network Controller"
4. Click "Update Drivers"
5. Click "Search for my own drivers"
6. Click "I will choose my own drivers out of the device list on my computer"
7. Two scroll boxes appear, in the left box select Broadcom (the maker of the airport card)
8. In the second box scroll down a little and find "Broadcom 802.11a/b/g Multiband-networkadapter", select it and press next.
9. Watch the bars progress, installation happen, and your wireless network icon on your taskbar light up with your network ready to be joined.
10. Smile, relax, make a coffee & join your network.
Hope that helps someone later down the line.
Warm regards,
-NickCG