DirectoryEntry oDE = new DirectoryEntry(\"LDAP://DC=Test1,DC=Test2,DC=gov,DC=lk\");
using (DirectorySearcher ds = new DirectorySearcher(oDE))
{
ds.PropertiesToL
Had the same issue and managed to resolve it.
In my case, I had an AD group in the current logon domain with members (users) from a sub domain. The server that I was running the code on could not access the domain controller of the sub domain (the server had never needed to access the sub domain before).
I struggled for a while as my desktop PC could access the domain so everything looked OK in the MMC plugin (Active Directory Users & Computers).
Hope that helps someone else.