GMS, try this next time you start up instead of disable/enable:
Assuming XP, click Start, Run then type CMD and hit ENTER key on your keyboard (or click OK)
type:
ipconfig /release
hit ENTER
type:
ipconfig /renew
hit ENTER
wait a few moments for the renew to occur - should see some numbers (IP address, DNS data....)
type exit and hit ENTER to close the cmd window.
If you are now online ok - you may need to change start-up order - powering modem earlier - or depowering/repowering modem when you start your PC.
Or there may be issues with your PC's TCP/IP settings.