The 4.x client is a virtual adapter compared to the 3.6.6 client which places a shim in the TCP/IP stack. I have seen these kind of problems before with the 4.x client on certain applications. I would say there probably is not a work around and to continue to use the 3.6.6 VPN client over the AT&T dial-up.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
[toc:faq]Introduction:This document describes details on how NAT-T
works.Background:ESP encrypts all critical information, encapsulating
the entire inner TCP/UDP datagram within an ESP header. ESP is an IP
protocol in the same sense that TCP and UDP are I...