OK so I found the logs on the client side... they said this...
Mon Mar 26 18:01:27 200] outgoing message ==> <?xml version='1.0'?>
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
<soap:Body>
<AuthRequest xmlns="urn:zimbraAccount">
<account by="name">xyz@closeconcerns.com</account>
<password>*****</password>
</AuthRequest>
</soap:Body>
</soap:Envelope>
(1182)
[Mon Mar 26 18:01:27 200] incoming reply ==> <?xml version="1.0"?><soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope"><soap:Body><AuthResponse xmlns="urn:zimbraAccount"><authToken>0_fa622997c4d f6d2d6d86eaf4e7a8c3823faf3ee1_69643d33363a63373736 636635662d376230632d346436342d613462352d3263306564 613039353266623b6578703d31333a31313735313330303739 3732383b</authToken><lifetime>172800000</lifetime><refer>mail1.zimbra.hostprogressive.com</refer></AuthResponse></soap:Body></soap:Envelope> (1182)
[assert] error: (null)
[assert] where: "ZimbraClient.mm", "-[ZimbraClient authenticate:]", line: 1663
[assert] error: (null)
[assert] where: "ZimbraHelper_main.mm", "Authenticate", line: 2270
does this clarify the problem for anybody?
the authentication seems to be intermittent...
Thanks
John