Netgear WRN2000 - Internet Drops Out Periodically

I'm currently writing this from a laptop. It can access the internet perfectly, with no dropouts and no speed issues. However, my desktop PC is a different story. When I purchased the PC, it came with a standard wireless PCI adapter which really wasn't doing the job. It couldn't pick up my router from just one story above, where my laptop could. I decided to buy a new wireless adapter that would hopefully fit the bill. Unfortunately, again it didn't pick up the router from downstairs. Trying a different tack, I purchased the Netgear WRN2000 as an access point that would increase the range of my router. I connected my PC to this after configuring and all was going well for a while, until now. Now, every 1-2 minutes, the internet will slow to a crawl for 30 seconds or so, and while comparing speeds via the laptop (connected directly to the main router) and via the PC (connected through the extender to the router), the laptop clearly has the speed advantage. This is more noticable when playing games on my PC, such as Call of Duty. Every 1 minute or so, the game becomes unplayable due to lag for around 30 seconds, and sometimes this happens constantly. I'm unable to work out if the WRN2000 has a problem, or if it's interference. I actually tried connecting my PC to my laptop via ethernet, and bridging the 2 connections, which seemed to work for a day or so, but now does not. Also, i'd be willing to purchase a new PCI wireless card if anyone has any recommendations for one that has a strong signal range.