Ehyup

I'm hoping you experts can help me with this frustrating (and mysterious) 
problem. I and my partner connect remotely via VPN with our work network a 
lot for some file transfers and to connect Outlook with  Exchange Server. 
For quite a while this worked trouble free but in the last 3 months or so we 
have been finding it very difficult a) to make a VPN connnection in the 
first place and b) to sustain the connection for more than a few minutes. .

I am using two different Acer Travelmate notebooks (running XP Pro). My 
partner uses a Samsung Q45 running Vista Pro (spit!). The office system is a 
SBS2003 box (without ISA) connected via a Draytec Vigor 2600+ router.

The most common connnection scenario is connecting from home. Here we have a 
Draytec 2800 router and and a Netgear Rangemax WPN802  WAP (usually with 
good to excellent wireless signal). There is no problem in getting an 
internet connection and with download speeds of 3.5MB or better and uploads 
of c650KB over a wired connection. There is some throttling when using the 
WAP and bandwidth can be halved.

We are using the native VPN clients (XP and Vista) and the VPN server built 
into Windows Server 2003 - no proprietory clients or intervening hardware. 
Both routers are set to passthrough VPN traffic with no active management. 
The VPN symptoms we experience are:

a)    the Vista notebook won't now VPN connect at all via WAP (though it 
used to) but will over a wired connection (with the occasional failure);
b)    the Vista notebook will make a good VPN connection using a Vodafone 3G 
dongle;
c)    the XP notebooks will make a connection intermittently but will often 
a) drop the VPN connection or b) stall continuing to transmit but with no 
reception;
d)    breaking and remaking the VPN connection will sometimes succeed 
immediately but, more often, will time out at the 'user id and password' 
stage;
e)    the VPN stalling'' happens a lot. It becomes apparent most often when 
Outlook says it can't connect or disconnects from Exchange Server. Checking 
the status of the VPN connection shows some upload traffic but no download.

As I said, this all worked fine until a few weeks ago - except with the 
Vista machine which was always tricky. Nothing in the home/office set up has 
changed in that time. It is tempting to accuse the Netgear access point 
because this is the most obvious and most frequent point of failure. Trouble 
is, I get VPN connection problems (but not so persistent) when my 
notebook(s) are connecting from other locations.

There have been changes at the server end of this connection. First, the 
router set up has changed. We used to have the Vigor set with all of its NAT 
and firewall functionality turned off (so it was just an ADLS bridge really) 
because we had a separate 3Com firewall. That used to crash a lot and, as it 
duplicated the traffic filtering functionality of the Vigor, we simply took 
it out of circuit and reconfigured the Vigor instead. At around the same 
time, we changed IT service providers and the new guys did some fiddling 
with the configuration (don't know precisely what). We have also had to 
install some Vista specific files to accommodate the new Vista notebook 
(again, I can't remember what exactly). And, of course, there have  been 
dozens of MS patches, fixes etc applied to the systems.

Sorry to go on at length - but it is very frustrating and very hard to 
diagnose. Anybody out there got any idea what the problem(s) might be and 
how I might set about sorting is/them?

Any help most welcome.

Paul