Have you try get the tech to check if your cable's properly grounded? I've very similar problems at my house when I first got Cable modem a few years ago. it took 4 weeks to found out this very small thing.
It's Sometime it was working fine and then it just went off with no reason! The signal light flashing, one light then two light then all light flashing none stop. Called AT&T/Excite Tech supports and they sended the tech to my house many time, each time they came Cable modem will works??? well for a few hours and then it stop again! :evil: Called again and upper level supports can't find any problem with signal???
Well, I was gonna cancel Cable modem and cable TV Both and the Cable TV's guy came by to pick up the digital box and then he said, I've got signal feedback from my cable??? :roll:
Anyway, he went out and check with the main box, came back with a big mettal rod and grounded my cable! Wow, what a difference! My TV's pictures look a lot better, my cable Modem lit up and never have any problem since!( Well,untill AT&T / Excite broke up!)
Just some thought! You may have the same problems and it may works for you. If you call again and ask someone to check if your cable, Cable TV & Cable modem's properly grounded? :?: It might help!
Another thing is, at cable's main box some where... as per Cable TV's guy once told me that, it was loose at the main spritter?
Hope this help and good luck.