I encountered this problem when one of my domain controllers kept rebooting due to a failing disk. Peter Hayden's comment solved my problem, but his syntax is for a Windows 2000 domain controller. For a Windows 2003 domain controller, you must add the FQDN of the domain controller after the "/options" switch: "repadmin /options dc.domain.com -DISABLE_INBOUND_REPL".
Inbound replication has been disabled by a user using the command:
“repadmin /options +DISABLE_INBOUND_REPL”, from the Windows 2000/2003 Resource Kit, or by Active Directory when it encountered a problem (typically Event ID 2103, Source NTDS General).
Re-enable inbound replication using the command:
“repadmin /options -DISABLE_INBOUND_REPL” or resolve related Event IDs.
, and the link to "EventID 1113 from source Active Directory" for information on this event.