It seems their must be some incompatability between the router and NTL, but they do claim compatability with some models and NTL.
http://safecom.cn/code/product/WR/SWBAR-5400/qig.htm
NB Linksys' good reputation was based on the older WRT54G/GS which run Linux and are compatible with 3rd party firmware. The new equivalent is a WRT54GL which has more memory than the newer standard versions, and still runs Linux.
I use an old WRT54GS v1.1 with Hyperwrt Thibor firmware