Preventing access of folder of role 1 by role 2 user causing 404 error

I set up a basic login page for user authentication, along with 2 folders.  Group1 and Group2.  I then created 2 user accounts using the Web Site Administration Tool, and assigned roles.  Next I granted access for role 1 to group 1, and role 2 to group 2, denying access to opposite folders.  All works well except when I try to access Group 1's folder from Role2, I'm getting the following error page.     "Server Error in '/WebSite1' Application.
The resource cannot be found. Description:
HTTP 404. The resource you are looking for (or one of its depende ...