Of course, il you call Motorola they're gonna tell you it's microsoft. If you call MS, they'll say it's Motorola. Gotta love those technical support
Ideally, you could try:
1)another computer with LW connected via the motorola modem to test if the problem is Microsoft
2)another modem borrowed from somebody to test if the modem is the problem (with your own computer)
3)connection to another ISP like via 56k modem (you can surely find AOL cds for free...) to see is Cox and/or the modem is the problem.
Good luck, you'll need it!