so iv had this problem with two wireless repeaters now. when im connected to just the router, i am able to access the internet. however when i plug in and set up the wireless repeater ( the latest one is a amped wireless sr300) it works for a few min and then i get a "DNS lookup failed" when trying to access sites. 
this repeater replaced a hawking hwren1. which would work for a few min and then lose the network. 
i believe this is a problem with our internet connection into the house, but could it be a caused by the router? (wrt400n) our isp says its not their problem and that its our router, but this is the 4th one in under a year



Software/Hardware used:
linkysis wrt400n, amped wireless sr30