Adprep was unable to check the domain update status. Status/Consequence Adprep queries the directory to see if the domain ...

Adprep was unable to check the domain update status.
[Status/Consequence]
Adprep queries the directory to see if the domain has already been prepared. If the information is unavailable or unknown, Adprep proceeds without attempting this operation. 
[User Action]
Restart Adprep and check the ADPrep.log file in the %1 directory. Verify in the log file that this domain has already been successfully prepared.

ADPREP WARNING: Before running adprep, all Windows Active Directory Domain Controllers in the forest must run Windows Server ... Adprep was unable to add member %1 to object %2. User Action Check the log file ADPrep.log in the %3 directory for more information. ... Adprep was unable to add the application-defined HandlerRoutine function that handles CTRL+C and other signals. Status/Consequence ... Adprep was unable to bind to any Domain Controller (DC) over Remote Procedure Call (RPC) in the Active Directory Domain %1. ... Adprep was unable to check the domain update status. Status/Consequence Adprep queries the directory to see if the domain ... Adprep was unable to check the forest update status. Status/Consequence Adprep queries the directory to see if the forest ... Adprep was unable to check the specified user's group membership. Status/Consequence Adprep has stopped without making changes. ... Adprep was unable to check the specified user's group membership. This could happen if the FSMO role owner %1 is running ... Adprep was unable to check the version of the operating system on the Schema FSMO %1. Status/Consequence Adprep has stopped ...