VPN: PPTP connection to ISA Server

I explained my problem already in an answer to another thread. But that one
was located in the general newsgroup thus I try it again in the networking
group:

I cannot establish a VPN connection from my Vista RC2 (build 5744 German) to
the our ISA 2006 over PPTP. The PPTP connections work fine with XP clients.
On the Vista client I use the same settings. I also tried out different
settings (especially authentication protocols, normally we use MS CHAP v2)
both on the server side as well as on the client but it still doesn't work.
If I monitor the traffic on the ISA server I can see the initiation of the
PPTP connection and exactly 30 seconds later the connection will be
disconnected. There seems to be no authentication request taking place since
we use RADIUS and no RADIUS packets can be seen on the firewall.

With the same Vista machine I can connect to other VPNs (not set up with
ISA) over PPTP without problems.

Therefore I assume that there must be a problem with the
PPTP-implementations either of Vista or of the ISA server or in their
interaction.

Can anybody confirm these problems or is there even a solution?

Thank you for any comments,

P.

 

Not sure what we're using, the default XP VPN settings worked fine, and
I connected with RC1 as well... but with RC2, I cannot connect to our
VPN anymore