Broadband Speed Drop

[#1]

Hey all,
Starting yesterday 26th Jan - my broadband speed has become like a giant slug who's just been told to take it easy by his doctor for moving too fast.
I've done speed checks and they all come back as a fraction of what it should be.
(I'm on an old F9 Homeworker Pro account)
My sync speed from my router (Netgear DG834v2) says this:
DownStream Connection Speed 4832 kbps
UpStream Connection Speed 448 kbps
Which to me - looks absolutely fine as it's around where it should be on a normal basis.
However, speed tests tell me something is really wrong - I can barely surf the web and anything beyond that is just impossible.
I've checked my Usage but I can't determine if I'm over my usage or not - the graph given isn't terribly easy to understand as it doesn't tell me how much usage I'm allocated and how much I've used.
So I go through BT's speedtester - first test (connected via F9/PN) - says that there's definately something wrong as my throughput is a fraction of what it should be, so it tells me to reconnect my router as 'bt_test_user@myisp' which I do (as bt_test_user@f9.co.uk).
When I do this - I can get no websites at all - not even the speedtester so I can't continue with the tests or checks.
I've got 2 PCs running through the router, both PCs are experiencing this slow-down of service, both have anti-virus, anti-spyware etc... and all are current.
I've made no changes to my BT line or microfilters or PCs - so I can't see why this would suddenly have dropped speed.
This is driving me nuts (or nuttier) as I can't even complete the required checks to determine whether it's my account and I've gone over my limit or whether there's something amiss with my line.
Anyone else have issues like this recently?
Cheers.
Z

[#2]

I've just had a look at your account and although you are now connecting at 4832, sometime recently your line connected significantly lower. This has in turn caused your IP profile to drop down to 250, so you won't currently be seeing speeds higher than that.
If you stay connected at 4832 your IP profile will increase again after around 3 days and your speeds will be back to normal. Have a read of this link for more information on how the BT IP profile system works:
link:speed

[#3]

Thanks Chris, appreciate it.
I will wait a few days and see if it returns to normal.
Just out of curiosity, would power-cuts possibly affect the IP profile as the router would be shutdown and restarted in quick succession?
Z

[#4]

Not directly but the effect of the power coming back could have causes something in the area to cause interference - like a street light restarting