There is always the chance that, even though you've done what you could to avoid channel overlap, devices are getting confused by signal strength. You'll want as much space between the two as you can get. Perhaps you could try using a different SSID for each signal as well.
My current setup
-Standard DLS connection with modem/router combined into one unit
-Another wireless router connected via powerlink
-Main router operates on wireless channel 11
-Secondary router operates on wireless channel 6
-DHCP disabled for the second router
-IP address for second router assigned manually
Now the problem I have is that there is a bedroom next to the main router that has constant wireless drop-outs, reports are that on devices, the user needs to keep disconnecting and reconnecting to the network quite regularly (every 5 minutes) so I'm guessing there is a problem with how I have set up my multi wireless access point set up. If any extra information is required then I will gladly comply because I really need a solution to this issue.
On another note, is it possible for me to tell if the secondary router is down without using a wi-fi strength indicator? Thanks for your help