Able to reproduce the problem on a brand new install

ENVIRONMENT: W2008 SP2, IIS 7.0
1) Deployed brand new 5.6.1 CE
2) Bumped up Trust to Full
3) Install AD provider with source
4) Go into settings, and bang you get that error

WHAT DIDN'T WORK:
Tried many combination of the following, error still didn't go away:
1) Chnaged to classic / Intergrate
2) Added impersonate

<identity impersonate="true" userName="Administrator" password="your admin password"/>
3) Changed AppPool identifty: Network Service, ApplicationPoolIdentity

WHAT WORKED (no exception in settings screen):
1) Changed AppPool identifty: LocalSystem Or Administrator of the box. It worked with both Classic and Integrated

WHERE's ERROR
Ran in debugger. Error is happening at Settings.ascx.vb.CheckPipelineMode at the following line:
For Each entry2 In directoryEntry.Children

 

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Ash Prasad
Director of Engineering
DNN Corp.