what WICs are these?? WIC-1Ts or 2Ts? if so, yeah, u can use a DTE-DCE cable and clock internal source and check the WIC slots, but since u say that the NIU works with the other WIC slot on some other router, it might be an issue with configuration on the present router or a bad WIC..
just check if the configuraiton and the IOS on both these routers are same...
Hope this helps.. all the best.. rate replies if found useful..
Raj