Linksys Wireless Router :: E3000 Data Rate Slows Down After A Period Of Time

I have just bought an E3000 router when my old router died last week.  I am having two problems:
 
1.  The data rate slows down after a period of time (long message trail elsewhere)

2.  I cannot see everything on the network.
 
I have several Win 7 computers, two win xp computers,  three NAS devices (linux based), and a printer sitting on the network, along with two switches to cope with all the traffic (not to mention iPods, iphones etc.)With my old router, I couold see everything plugged into the network from my main Win 7 computer. (note:  the win 7 network map does not always work, but the windows explorer window of the network always showed everything).With the E3000 router, I can only see 1 or 2 of the devices on the network.  If I reboot the router, then sometimes all of the devices appear on the windows explorer window (sometimes not)I am running a workgroup (not a domain) and i am not using win 7's homegroup because that will not work with the non-win 7 devices.Is there a setting that will see all of the devices in Win 7 (either on the router or on the computers). I suspect it is a router issue as it worked with my old Zyxel router.