[Users] L2TP+NAT-T BAD_PROPOSAL_SYNTAX

When I try to send L2TP over IPSEC i got a BAD_PROPOSAL_SYNTAX from freeswan. The client is nated. I use SSH-Sentinel. When I connect without L2TP everythig goes right.
To make the L2TP connection I add the lines:

leftprotoport=17/1701
rightprotoport=17/1701
type=transport

and i remove the line leftsubnet...

I get the same message when I try to connect with MSL2TP/Win98 client after modifying pluto to accept 17/4500 in phase 1.

Hope someone can help...

Thanks in advance..
regards

Carlos.