Dropped broadband connection (LAN)

I am hooked up to a T-1 line via an ethernet card in a
shared office center, and find that while I have a
connection to the router, I cannot connect to the
internet at startup about twice a month without
restarting 2-3 times.

More Recently the internet connection seems to "time out"
after about 5 minutes although both the router and my NIC
show a connection is in place. I can regain a connection
by disabling and enabling the network connection.

This is extremely frustrating

System is WindowsXP Home on an IBM T22 thinkpad.

Any Help out there???