Well this problem doesn't occur to me. I am using 32-bit Vista.
But the ones that it occurred to (at least two of them) use 64-bit Vista.
This is what sweatyfish told me:
is this only happening on x64? i know 64bit has issues sometimes with the alpha transparency of styles made on 32bit. I would suggest opening the resource in paint.net, add a new layer, merge down (flatten) then resave it as a 32bit .png. Then import it into VSB.
From what I see, it looks like an x64 issue.
Anyone know about this?