bizarre wireless internet problem

Something very strange is going on with the wireless internet connection in my house. All the basic diagnostics have been done, the router has been replaced and all the normal steps have been taken to make sure this is not something wrong with one computer or device:

The wifi very reliably cuts out every 10 minutes from around 10am to 8pm. I can be using the internet and watch the clock as pages stop loading, Pandora stops playing or games go 'connection interrupted' at 1:05, 1:16, 1:26, 1:36, 1:47...all afternoon. After 8pm the connection will be perfect for streaming video/online games/downloading files all night long. All indications show that the signal strength is strong, but the connection is unusable both for intranet and internet purposes. Turning the computer's wireless card off and immediately back on cures the problem instantly.

I'd imagine it's an interference issue, but I can't for the life of me figure out what is causing it, so I figured I'd come here for ideas. We've tried every wifi channel. Our house is on a double lot in an old neighborhood, so the neighbors are pretty far away to be causing this kind of interference. The very strong signal right next to the router cures the problem...but the wireless must serve computers throughout the house.

I've considered:
- Wireless phone (we don't have one)
- Xbox 360 (unplugged)
- Microwave (don't have one)
- Other wifi devices (none)
- Baby monitor (don't have one and neighbors don't have little kids)

The real question: what kind of device would so reliably cause interference every 10 minutes, but only during the daytime? Really weird.

The electrician is coming soon to run ethernet around the house, but I'd love to be free from the wires sometimes...

 

Hmm good ideas we have an air conditioning system that only runs during the day that could be causing the problems. I'll experiment. Thanks!

(and yes I've played with the DHCP leases to no end...no dice)