router connection problem

Hi

I am having network connection problems, and thought I'd see if anyone
else has had this problem before:

I have a mn700 router connecting my cable internet to a pc, and xbox.
It was working fine, up till 2 weeks ago when my cable modem (toshiba)
went out and the cable company brought out a new scientific atlanta
modem. If I run the cable from the modem to the pc, it works fine,
connection very fast, seems normal. If I hook up the router with a
wired connection to the pc, the internet connection will work about 1
or 2 minutes very slowly, and then stop. I thought it might be the
router, so I bought a new linksys wrt54g, but it did the same thing.
Just to make sure it wasn't the router, I took the linksys back, and
picked up a new netgear router, and it did the same thing, maybe 2
minutes working, and then nothing. I tried using 2 new cat5 cables,
but it didn't help. The cable company said since the internet
connects just fine from the modem to the pc, it isn't their problem,
but they are supposed to send a truck out to check the signal strength
of the line some time this week. Could that be the problem? Anyone
have problems with scientific atlanta modems? any advise would be
appreciated.


Russ