TranslateName relies on the SamAccountName property on the AD account. First use LDP.exe to review the object you want to lookup. Make sure that the SamAccountName matches what you are using as the name to query. Make sure that any new objects like new user and computer accounts have time to replicate fully.
Have you examined the error codes returned by TranslateName? Did the INIT fail or the SET fail? If these two succeed then the GET should have no problem.
