When will Folder.Size not work in VBScript

Question

http://stackoverflow.com/questions/3871260/how-to-get-the-size-of-the-network-folder-in-asp

I have mentioned my problem on the above link and so far I have come to the conclusion that possibly a Folder has been given Protection rights because of which I cannot get it's Folder.Size in vbscript using FileSystem object.Can anyone shed light on this.