Access denied error...sort of

I have several users trying to connect to an existing mapped drive. The problem is when they click on the shortcut they get access denied. BUT, if they go through the folder list they can browse the entire drive no problem. This problem is with multiple users connecting to multiple drives so I don't think it's share permissions on the servers. And they were able to access the drives with no problems as recently as a week ago. As far as I know nothing has changed, but that doesn't rule out some sort of mystery patch being sent down the pipe. Thanks in advance for any help with this.