routers compatible with readynas duo

Any wireless router will do. But I will recommend a NETGEAR one. :)

I replaced my WRT54G router with a refurbished Netgear WNR2000 that I got off Newegg for $22. (Currently $39 with shipping). I also included in the system a Netgear GS108 switch since the router ports are only 100Mb/s (as are the ones on the WRT54G). This way, my wired PCs and the NAS units benefit from the gigabit speed of the switch. (Only my printers are directly connected to the router).

You might want to try a direct connection test to make sure it's the router, not something in the NAS. Of course, if you would benefit from a change from b/g to b/g/n then an upgrade would help. Unless you buy a new router that has gigabit ports (1000 Mb/s) rather than the fast ethernet (100 Mb/s) and you are using a wired PC, consider a gigabit switch in the network rather than changing the router.