Sudden drop in sync speed by 50%

Since last Sunday (11th May) my sync speed has dropped from ~8-9Mb/s to a consistent 3.8Mb/s. Now whenver my modem recconencts it always hits exactly the same sync speed of 3,837 Kb/s.

I have tried various filters, wirelass vs ethernet, master socekt/test socket etc and nothing made a difference so I suspected the Be Box was faulty, however tried my box at my friend's house and it worked at 8Mb/s no problem (and he has a higher attentuation of 47db vs my 41 dB.

Sicne the cut in speed I aslo notice that FEC errors have increased dramatically (see stats below). My friend suggests two issues:

1) I have been put on a lower speed profile at teh exchnage - can anyoen explain the implciations of this?

2) About the same tiem as teh speed drop, the main road near my house started being ripped up in order to be resurfaced. They've taken the tarmac layer off and are due to resurface it - could this cause problems with the lien speed/interference and why? I did a BT quiet line test and couldn't hear any noise, clicks or static.

Thanks for any help that can be given.

Has your noise margin changed (e.g. from 6dB to 15dB)?

Can you plug into the test socket inside your BT master socket, to see if there's any improvement?

Noise margin - I have trie dvarying with DMT tool - but not much imapct. I get3.8 Mb/s with 6dB (default)

and yes tried the test socket