I've found the problem. WinXP tries to negotiate an encrypted channel by default when it is a member of a domain. To disable this, use the Local Security Settings editor, and find and disable this key: Domain member: Digitally encrypt or sign secure channel data (always) This will remove the 30 second delay. Note that this is only a problem if you are a member of a domain - if you are not joined to a domain, this setting has no effect. Thanks all for your help.