When i got my new computer with vista i had the EXACT same problem, so you are in luck! Go to my computer, The C drive or w/e you have, then drag the Blockland folder onto the desktop, then try to open it, then it should ask for permission etc. then when its open just open all the sub-folders and then try to run the game!
*all you have to do is open the folders, nothing else, this should give access*
Hope this helps. =D