[pptp-server] Can't connect on first attempt

[James Pearson]

I have a strange problem when I attempt to connect to my pptpd server
(pptpd-1.0.1, ppp-2.3.11+openssl-0.9.5-mppe.patch, Redhat 6.2, 2.2.16-3
based kernel) using any Windows client over a dialup connection: 

Dial up my ISP, dial up my pptpd server -> fail with a connection failed
error (629)

Any subsequent attempts to connect, fail with the same error.

However, if I then disconnect from my ISP, reconnect to my ISP and dial
up my pptpd server - it works fine. I can then disconnect/reconnect to
the pptpd server as many times as I like...

I've tried a number of different ISPs, various flavours of Windows
(95/98/NT4) clients and a complete fresh install of Linux/pptpd/ppp on a
different box - but I can only connect to the pptpd server after my
second ISP dialup ...

The only common element is that the pptpd server is behind a firewall
running Firewall-1 - could this be the "problem"?

Any help would be appreciated.

Thanks

James Pearson