Function: GetGuidForServer. The error usually corresponds against a probe being run on Active Directory. The cause is that when the tool or the individual dll is loaded, not all the right permissions on the account were present. The load process reports successful completion, but using the dll will cause the failure.
Unload the dll, and then logon to the system using an account with the appropriate permissions. Reload the dll, and then the probes should be able to access the Active Directory Resources.
Normally it can happen with AD monitoring tools that use IADsTools.dll replication module, for me it happened on Tivoli Monitoring for Active Directory.
Function: DsGetSiteName, Error: 1707 = "The network address is invalid." - no additional info.