OK, it finally worked after I went to
Device Manager / Network Manager / Update Drive Software.
First time Microsoft drivers worked over the manufacturer's drivers. :p
What's with that? I don't get it. Why did this bug appear on the DIR-645 and never appeared before? Was there some type of IEEE protocal update that ASUS did not keep up with? Or perhaps they kept up with it but broke something else with their driver release that only affected newer devices (on Vista)?

Anyway's thanks for all the help everyone provided. For the record, this is my motherboard. The problem area was the
Realtek PCIe GBE Family Controller.
ASUS P8P67 (REV 3.0) LGA 1155 Intel P67 SATA 6Gb/s USB 3.0 ATX Intel Motherboard with UEFI BIOS
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131705