Hi there, I'm Tim and will do my best to assist you. Couple of questions. Does the Macbook work just fine when connected to the main wifi, or other wifi networks?
Ok, can you give me the model numbers of both the belkin and the extender?
Ok, in my experience WIFI Extenders are touchy if they are not the same brand as the Mode. I've seen this a few times where for what ever reason some devices do not play well with odd paired extender and router. Your router is a pretty obscure one, especially in the US. Belkin and Netgear seem to be the most choosy of the device brands regarding paring well. I'm not telling you to get another router or extender, but if they were made to work with each other, that would rule a few things out. One thing we can do is
One thing we can do is, either have you look into the config page of the extender and post back here, or I can remote in and see if anything jumps out. As far as a possible configuration problem, a machine jumping on and dropping could be it getting an IP then being kicked by something else that wants that IP, the logs should have this info.
This sounds like one of those tricky problems that will take some investigation, i can only do so much with out looking at it. So i think the best solutions are A, consider getting a Belkin Router to at least test with, i know that doesn't make a ton of sense, B let me or someone else take a look via remote session at the config, and go from there. May need to review the Macbook, but i really doubt there is anything going on with it. I hope this makes sense.