my tiscali broadband at work keeps dropping out

the modem signal will go to red before restarting and trying to reconnect/intialize

every now and again
the laptop will tell me that the usb bandwith needs adjustment via the modem

i need to remove all over usb devices while it adjusts, but there are no other devices present

sumtimes this is sucessful, sumtimes not

any ideas?
tried a new microfilter on the phone line with no joy

modem is a sagem Fast 800-840