It works as advertised on my Windows 7 laptop.
However you have Vista - which apparently had some problems with its "UAC" - Seven is supposed to be better, and you can also turn UAC off in it if desired, which Vista
apparently cannot do?.
But something to do with how Vista's UAC is (mis)behaving is probably it.
If there is a way to turn it off in that O/S then give that a go and see if the problem goes away.
As to why it worked before and not now - have you applied any patches and so on to Vista in the meantime or tweaked O/S parameters etc?. It's a
Microsoft Operating System after all, so don't expect it to do things the same way on different days of the month

!
Oh - and what directory path Microsoft thinks should be "managed" (ie mangled!) post Vista can be odd. I copied some file into the c:\ root folder on seven once and then could not edit it since it had been copied from a network file folder and it had "carried across" some sort of internal flags that could not be turned off despite my efforts with the various M$ utilities. However I then discovered that if I copied it instead into say c:\zzzz then editing was allowed perfectly happily. So strange things can happen, depending on the particular path you use in Vista/Seven with UAC enabled. In other words -
look at the folder your game is installed to, and maybe try changing that path. Microsoft UAC weirdness is often related to your directory path.
Andy