Getting stuck on 'checking username and password'

[krysia]

I'm actually pretty happy with my F2S service - I've had good and helpful advice from staff on the LLU phone line and timely replies recently to issues that have been logged, so things seem to have improved greatly in the last few months. The problem I'm having is more of a niggle: I have a Billion 7402VGP router and usually have a stable connection all day until early evening; my speeds are around 5 megs, and I usually get 83% of that, according to the DSL Zone custom speed test. However, usually between 5 and 6 pm, I lose my connection even though the ADSL light stays on. At this point the router says 'checking username and password'. I thought the problem was being caused by a low SNR margin and got advice to change the coding gain to 7; this now keeps my SNR margin respectable, but the problem still happens and I need to restart the router to get reconnected. I contacted Billion about this and got the following reply:
'With regards to the drop in connection then it hangs on checking username and password, it could be caused by you ISP's login server not realizing that you have login off and therefore you cannot log back in straight away. This is quite unusual as we have a freedom2surf line here in our lab and we have not had that problem before but we mind you that line is not running ADSL max just a standard 2Mbps line. The only time we have experienced similar issue is on a ADSL 2+ line with another ISP as we had the same problem of not able to sign on and getting stuck on checking username and password. We had this issue fixed after checking with our ISP.'
So, is anyone else experiencing problems when their router tries to resync automatically? (Very occasionally, mine manages to do so, but 99 times out of 100 it hangs as described above.) I'm on the Brixton LLU. I find that I can preempt the problem if I notice the connection slowing down: then I click 'apply' on the router ADSL page which causes a manual resync that takes only a few seconds, but it would be nice to get to the bottom of why the automatic resync fails to complete the logging back in.

Thanks for any help you can give me.