A small office with four computers and a RTA1320 adsl2+ router.

I needed to check my own router, RTA1046VW, was OK so brought it in and connected to one PC and adsl line to check it's line speed - excellent connected at 3500/160kbps. 

Reconnected original router and checked the router status pages - shows U/D as 3500/160kbps.
Running speedtest.net or similar on any of the machines gives results like 64kbps at which point I go get a coffee! Before I swapped the router in/out the connections were fast but now everybody wants to kill me!!

I've tried:
- turned all equipment off/on
- tried only having one PC on
- Tried "repair" on LAN support  tab
- reinstalled NIC drivers on one of the PC's
- swapped cables from hub to directly into router

None of these has improved the speed. Does anybody have any other ideas please.