How to find an user on a LDAP server

When trying to find an User on a LDAP Server, I get the following error "Unknown error (0x8000500c)"

This is the code I'm using:

PrincipalContext domainContext = new PrincipalContext(ContextType.Domain, "gandalf.intrafg");
UserPrincipal p = UserPrincipal.FindByIdentity(domainContext, IdentityType.SamAccountName, "Consultor1");

Indidentally, the following piece of code seems to work (no exception is generated), but the samAccountName comes through as a byte array. Anybody knows why?

DirectoryEntry entry = new DirectoryEntry("LDAP://gandalf.intrafg");

DirectorySearcher searcher = new DirectorySearcher(entry);

//searcher.PropertiesToLoad.Add("givenName");
//searcher.PropertiesToLoad.Add("sn");
searcher.PropertiesToLoad.Add("samAccountName");

searcher.Filter = "(&(objectCategory=person)(samAccountName=Consultor1))";

SearchResult result = searcher.FindOne();

Your second code block works just fine, I however did not pass the domain name in the DirectoryEntry initializer.

    Directory entry = new DirectoryEntry();
//other code
result.Properties["samAccountName"][0].ToString();