Looking at your benchmark results and reading this
it certainly seems that you have a 64 bit card. Where did you find the information your card should be 128 bit? It's very suspicious that I could find almost no information about the V9520 memory bus. Just the link above presenting a table in the bottom of the page claiming that all 128MB V9520magic cards come with 64 bit
It's a very irritating policy to hide product information from consumers, IMO.
EDIT: Oops, wrong link above, sorry! I meant this
webpage instead. In the bottom of the review is a table claiming the card has 64-bit memory bus. Doesn't seem too reliable, but it was all I found...