The reason you are getting the access denied is the permissions are set to allow a specific group in, and the techs don't belong to the group. Therefore they aren't going to be given the opportunity to connect to the resource. The dialog box you are speaking of where it asks for username and password occurs most commonly when you try to connect to a resource that is on a server/workstation that isn't a member of your domain (i.e. a stand alone server). The box appears because NT/Win2k is unable to find a user account matching the one you are logged in as, therefore is doesn't "know" you, and will then prompt you for id. The access denied occurs because NT/Win2k finds your username, and then can find out which groups you belong to, then it compares your group membership to the permissions on the shared resource.
I know this sounds rather confusing, but trust me I know what I'm talking about. Where I work all 14k users belong in one domain, and each of the 100 departments has it's own resource domain. If I don't add the correct group to a resource domain, then the dialog box appears asking for username and password, and my users don't know what to do.