SymptomsColdFusion was installed on the server. After Plesk installation ColdFusion administrator website started to prompt with authentication window.
CauseMost likely the reason of the problem is missed permissions on ColdFusion folder or files.
ResolutionMake sure that C:\ColdFusion8\runtime\lib\wsconfig folder has Read and Execute permissions for Network Service which is used by ColdFusion application pool.
Make sure Read&Execute, List Folder Contents permissions are present for IUSR_<COMPUTERNAME> on C:\Inetpub\wwwroot and its contents.
Note: <COMPUTERNAME> above must be replaced with your real computer name.