L2TP-IPsec EAP-TLS Fails for Vista, Works in XP

Hi All,

I have a MS VPN test environment setup with the following configured:

L2TP-IPSec EAP-TLS
L2TP-IPSec PSK
PPTP

All three methods work fine under Windows XP.

L2TP-IPSec EAP-TLS does not work Under Vista, but the other two do.

I receive the following error when connecting via Vista:

Error 788 - The L2TP connection attempt failed because the security layer
could not negotiate compatible parameters with the remote computer

I have confirmed that both my computer certificate and user certificate are
valid. My CA is in Trusted Root CA's.

My CertSrv has been updated to use the Server 2008 Beta 3 pages per the
directions at:

http://support.microsoft.com/default.aspx/kb/922706

Again, XP works fine for all 3 methods, Vista doesn't.

I've also tried enabling L2tp "Weak Crypto" via the registry setting pointed
out at:

http://blogs.technet.com/rrasblog/ar...scenarios.aspx

No go.

Anyone have any ideas what's going on here? Are there any known documented
incompatibilities between Vista and 2003 IAS Based EAP-TLS VPNs?