Socket Error # 11004 Help please

I have recently ported from Delphi 5 Professional with the Indy components
to Delphi 6 Professional.
My programme worked before but now gives me Socket Error # 11004 when trying
to IdFtp1.Connect, however if a connection to the Internet has already been
established then there is no error and the ftp proceeds.

Does anyone know what changes in D6 could cause this or what I should have
done that I have not ?
Also where do I find the Socket Error code definitions ?

Any help would be appreciated
Thanks George