Why is my VPN not working?

Struggling to get an answer to my VPN troubles. I did have it working a few days ago, had been solid for a year. Here’s the log entry for a L2TP connection

Thu Apr 29 09:56:18 2010 : Directory Services Authorization plugin initialized
Thu Apr 29 09:56:18 2010 : L2TP incoming call in progress from 'xx.xxx.xx.xxx'...
Thu Apr 29 09:56:18 2010 : L2TP received invalid message (expected SCCRQ, received Hello)

These line repeat and it appears as if there are five incoming requests as we get five hangups:

2010-04-29 09:56:18 BST	   --> Client with address = 192.168.1.23 has hungup

(repeat five time with different IPs).

PPTP also fails to connect, different error in the logs, want to see those?

Any ideas?

DG