Diagnosing a colleague's broadband problem, probably line related

[#1]

So I 'm trying to help out...
First things first: Desktop running Vista, old Solwise SAR110 router, two BT branded microfilters, Plusnet broadband.
Symptoms: First problem is something like "WAN PPPoE Miniport" device problem. Looks as if Vista has tried to create a broadband connection. I've tried to explain about routers...
Second problem: Router goes through usual motions of synchronising, stays in sync for about a minute I think then drops sync. Oddly enough this doesn't seem to have affected the line profile as it's a full bore 8M connection and SNR between 10 and 15dB.
Tried the 110 at home, works fine at 7136k. Going to try alternative routers, wonder if the SAR can't cope with it that good or maybe I have to set up some attenuation somehow. Out of practice at tweaking the 110.

[#2]

WAN PPPoE Miniport  don't know if this is relevant, but we use PPPoA.

[#3]

It looks as if Vista is trying to create a dial up connection. Make sure the network connection is set up correctly and never dial a connection is set in IE. Make sure there is no dial up and do the old ipconfig /all to ensure its getting an IP address.
If the route is ok at your house then you would suspect a line problem. Remove all the phones and plug into the test socket and see if that sorts it out

[#4]

Master socket test failed with the 110. I've got a couple of alternative routers to try, a Draytek Vigor 2600 and a BT homehub.
Wondering whether to raise a ticket now or wait tol after.
Figured the WAN miniport was windows trying to be helpfull, deleted it.
Anyone know why Windows is so dumb about LAN connections? I'm getting tired of computers repeatedly showing "No connection is available" when connected via a router, anyone know a fix?

[#5]

Hopefully resolved, I tried the homehub and that worked first time. Didn't think to retry the 110 though so I'll probably never know if the problem had gone away by itself.

[#6]

I have an old SAR110...  and for many years kept it on the line purely because it has one of the best CLI's Ive ever come across.  I put it on my own line when I was first maxed purely because of its advanced logging (and some other techy) features... with another router purely acting as glorified wireless access point.
It has no problems what-so-ever maintaining a solid 8Mbps sync.

Obviously Im not certain but I suspect that the problem may be more to do with perhaps the way which it was set up on the XP machine for networking and whether it was set correctly.
Is is possible that it syncs up correctly, but when you try to surf or get mail.. something on the XP machine tries to establish a connection via another means which knocks the SAR offline.
Theres also something else to look at - and thats that the SAR110 by default has a ridiculously low Maximum IP connections set by default.. which can cause what looks like the connection to drop.
Try increasing to maxipsess = 512...  See http://www.kitz.co.uk/routers/errors.htm