Hi there, and welcome to the forum
I'm going to leave the issue of the router locking up for now, as this is probably unrelated, and try and concentrate on your line quality.
Forgive me for trying the simple stuff but:
~ Make sure everything is filtered properly (sky boxes, fax machines, telephones, alarm devices, etc)
~ Try swapping the filters around / changing them for spares if you have any, and see if that helps.
It sounds like you have interference on your phone line from somewhere. What the interference is from, is hard to say.
A SNR of 26dB is very good for your attenuation given that you're on 1Mb (the higher the speed, the lower the SNR becomes, due to cramming more data onto the line). SNR can go as low as 2-3dB and maintain a connection, if the rest of your line is fairly stable. Other people have problems if it goes down below 6-7dB if the line is longer or is susceptible to interference. It's hard to say, but generally a SNR of 6 or above is considered to give a reasonably stable service.
Apart from what you said (the SNR drops after a couple of hours) are there any other patterns to it? I.e. do you always try at the same time of day? Does it ever go back up again without a re-sync?
As for your CRC errors, over what period of time do they accumulate? 100's of errors that gradually increase over a few days is nothing really to worry about. However if you get short bursts of errors where they grow by a large number over a matter of seconds or minutes, this would probably indicate either a fault with the line, or interference coming from somewhere.
Do these errors coincide with your central heating / fridge / freezer switching on/off or anything like that?
Unfortunately, I'm pretty certain that BT won't class this as a fault.
I would have said to use a filtered faceplate but since you already are doing, there's not much point. Unless the filter on the faceplate has deteriorated somehow, over time. If you have an adapter or a microfilter handy (or even an old 56k modem lead), you could take off the NTE5 front panel and try plugging into the test socket behind it, to see if that makes any difference (just unscrew the front panel and you'll see a BT socket there). If that makes things all better, a new faceplate is probably in order.
There is another thing that may help, but I'm really not sure of its degree of effectiveness when combined with a filtered faceplate. It may not even help at all - I don't know, merely offering a suggestion.
Phil T has posted up a tutorial about disconnecting your ring wire. This effectively prevents this wire (which is useless if you have ADSL anyway) from acting as a large radio aerial and picking up all sorts of interference from around your house. His tutorial is
here if you fancy having a go, and his
next blog entry shows two frequency graphs - one with the ring wire connected and the other with it disconnected.
My own line has a nasty habit of showing 25+dB SNR sometimes, yet it can go down as low as 14dB at other times. I haven't quite worked out the rhyme or reason for it, because up to now I haven't really needed to. Like you though, I'm getting a bit more anxious about it as MaxDSL looms!
I am going to try the ringwire trick myself later on today to see if it makes any difference. I don't have a filtered faceplate though, so I'm expecting to get slightly better results.
As regards your router locking up, this could be down to it's DNS cache getting full. If you use your ISP's DNS server instead of your router, this can help alleviate some of the load on the router, and stop it locking up. I've seen this with a D-Link router before, in fact a lot of routers suffer from this problem. At the bottom of
this page it shows you where to set your DNS settings on the PC, if you're not sure.
Hope this post gives you some food for thought, please let us know if you get any joy, or even if not, and we can try and take it from there