To killerz298:
I don't know whether your periodic router reboots are related to the poor wireless performance you are experiencing. Assuming these problems are not related, you might investigate whether the problem is in the other device, since two ends are required to make a wireless link.
Regarding your interference question, I'd be surprised if any household source of radio-frequency interference (RFI), other than a microwave oven, would be so strong that it could overwhelm a 2-3 foot 802.11n link, provided that both devices are working properly. However, if you do suspect RFI, there are a number of ways to go about troubleshooting. Assuming you have no instruments, you could start by eliminating potential sources of 2.4 GHz interference, such as microwave ovens, portable phones, cell phones, computers, light dimmers, chargers for battery-operated devices, anything with a switching power supply, and the like. You may need to remove power to these devices completely (including batteries), because some actually continue to operate despite ostensibly being turned "off".
If I were doing this, I would find the circuit breaker for the circuit that powers the router, and the next time the wireless link appears to be sluggish, I'd turn off every other circuit in the load center (fuse box). Then I'd unplug and turn off everything else connected to the circuit that powers the router, and shut off any portable phones and cell phones. That should rule out RFI sources in your own home. If the router's wireless performance immediately returns to nominal, then you can start plugging things back in and turning breakers back on until the problem comes back.
If the problem does not go away, either it's not caused by interference, or the interference is coming from outside your home. RFI, like other RF, goes through walls, floors, ceilings, roofs, etc. (unless they contain metal, foil, or mesh). This is more of a problem in multi-unit dwellings than in detached single-family homes.
Best of luck and happy New Year!