Has it been playing about like that all the time?
I started noticing significant lags during online game 2 days ago. No significant changes my end that I can think of. Ran every BB speedtester under the sun since then and all with same results - flickering needle like a Cessna's ADF!
Same results from 2 different laptops connected wirelessly also, one Vista, one Ubuntu.
Have you left the modem (or modem/router, or whatever) switched on all the time?
During the 12 day settling in stage the router has been reset a few times times. First during the first day of connection when I was comparing speeds on my extension sockets to the master socket, and then from the various sockets after I disconnected the bell wire from the master. It had then been running uninterupted until I started troubleshooting 2 days ago.
Have you checked the theoretical speed of your line?
3Mb based on distance from the exchange, that was BT's estimation after checking our line also. Over the past 12 days I've been running BT's speedtester program and have seen my IP profile as high as 3Mb and enjoyed up to 2.8Mb out of that with no noticable problems. My IP profile appeared to be changing daily though - sometimes as low as 500kbps giving me about .42 downstream.
I have just had a 30 minute call centre experience where they first ran various line tests involving lots of disconnections and them calling me back - then they attempted to remote access my PC which I was willing for them to do but they abandaned that idea and ran more line tests.
A BT engineer is coming out on the 11th. I asked if they found any problems with the line tests and they said everything seemed OK and an engineer was required to physically check my setup etc.
I was also advised NOT to call them back before the engineer arrives regarding this problem as it would wipe all their records and ticket history and it would all have to start from scratch. Never heard that one before!