Hi there,
I had a similiar problem when we got out first 3 modem in December 07. We tried everthing to get it to work, spent hours on the phone to their helpline, even had an engineer come to the house and brought out pc back to the shop where we purchased it thinking that might be at fault. There were no answers. Then hubby spotted that they had a newer model around Feb/March 08 ( a black modem), they were happy to swop it for us and we had no problems at all with this one....
When did you get your modem? Is it black ?
I'm in work at the mo- but can check out the model number when I get home.