Faulty routers?

I live about 5-6km from the exchange and had stability issues last year which were resolved after the 5th or 6th BT engineer visited. Since then I've had a stable connection at around 2000 sync speed. Not great, but that's about the best I'm going to get at my location. Here's a link to my issues from last year http://forums.thinkbroadband.com/notspot/f/4035519-a...

On 16 May this year (i.e. 3 days ago at time of posting) I lost internet connection for 15 mins. I had in the back of my mind that BT were going to do some work according to SamKnows. My exchange is being upgraded from ADSL2 to ADSL2+ (no infinity for a few years yet). When my internet connected back, I had double the upload. I've never seen my upload speed great than 448 before, but it was at 800+. Also my download sync. speed was at 3900. I was pretty excited that I was going to have decent speed. However from that point on, half the internet sites I went to did not connect with errors like this: 
YouTube
http://screencast.com/t/eWxTDvbGBza

Uploading an image to WordPress
http://screencast.com/t/phXpSBKthx

Speedtest.net looks like this (I have flash installed)
http://screencast.com/t/KK23hn0lUn

IG Index http://www.igindex.co.uk/login/
http://screencast.com/t/4BlBO3fR

My router stats looked like this at the time:
http://screencast.com/t/BVKXds8MOL2

I contacted my ISP (Vivaciti) and they said it might be an MTU issue. I tried to reconfigure my MTU from 1500 to 1432, but the router would not save the setting because the username was wrong. The ISP was very surprised at this and suggested that my 2Wire router may not be compatible with ADSL2+. However I do have an old Netgear 834 v4 router in my drawer, so I plugged that in but it could not connect at all.
When I plugged the 2wire back in a few hours later, my sync speed dropped to this where it has remained ever since:
http://screencast.com/t/EjqLmtVS

BT visited yesterday and told me that there is nothing wrong with my line and said the router was "a bit hot", and ordered me a new router. Having had 5-6 BT engineers last year with only the final one resolving my issues, I do not have much confidence in these people. Do you think it really could be an issue with BOTH my routers? Do you think that the possible upgrade to ADSL2+ has caused my 2wire router to stop working? I work from home a lot so I'm pulling my hair out yet again. Thanks for any insight.

Hi,
As discussed on the phone with one of our customer services staff, you had to separate issues, one was a faulty port in the exchange that was reset and the other was with the routers, you brought a new router over the weekend and that one is working fine, so looks like (and did seem unlikely) that one router would not allow you to change anything in it and the other would not connect.

I have to say that Vivaciti support is top-notch. They were able to diagnose the problem very quickly and replied to my email to them in tech support within 5 minutes. Can't get better than that for support. My line is fast for my location too.

Thanks Vivaciti!