NortelnetwksVPN connectivity proble: Loginfailure dueto:Driver fai

I am trying to connect to my office computer thr Nortel contivity VPN Client
Software,It was fine two days back but i am getting the following error from
today.
the error i am getting as" LoginFailure due to river failure"
in my eventlog viewer for system i got following message:
"The server could not bind to the transport \Device\NetBT_Tcpip
..............."
in the nortelorks folder error log has this message
"Unable to complete encryption handshake with remote side. Encryption
Mismatch."
Login Failure due to: Driver failure
also many other processing messages.
i reinstalled my vpn software and tried again but still getting same
preoblem ,
Anyone's help will be appreciated.

Thanks
--
msl