Slow T1 Connection

I’m having trouble with our company’s T1 connection.
We recently moved to a new building in a different city. We ordered a T1 line to be installed before we moved.
If I plug the T1 Ethernet connector to my laptop, I get about 750Kbs downstream.
But if I use any kind of router, I immediately take a performance hit and the speed drops to 230Kbs.
I’ve tried a Linksys/Cisco RV082 router, and several others (D-Link, etc…) with the same results.
Does anyone have any idea what the problem could be?
Thanks.