Possible Wi-Fi interference?

Before I start, I just want to clarify that I've tested this problem on 3 different machines (2 gateway laptops with built in wi-fi, 1 homebrew tower with PCI wi-fi card), 3 different OSes (XP, Vista, Ubuntu-variant), and 2 different hardware routers (1 year-old D-Link WBR-1310, brand new TP-LINK TL-WRT541G). It is consistent across the board. I have TWC/RR in Orange County, CA. My network is the standard issue cable modem directly into the wireless router, dynamic IP, WPA/PSK security.

I first noticed this problem with YouTube videos and other flash-based streaming services. The buffering bar would just stop and the video would halt. Depending on the sophistication of the individual flash app, getting it started usually involved dragging to seek bar to elsewhere in the timeline and then going back. This would restart the stream. Also, note that this was not accompanied by any network dropout... the wireless remained connected and I could continue browsing in other tabs (in fact, this would sometimes "kick start" the halted stream). Between these drops the network behaves at full speed. After finally replacing my router (my first guess) I tested again with similar results:

Ping tests (300 at a time) over the wireless connection to yahoo.com and google.com result in 2%-6% packet loss on every machine. I ran the same test WIRED and it resulted in 0% loss. I did this test on two different routers. So this leads me to believe that I am experiencing some kind of wireless interference that is disrupting my connection for a few milliseconds at a time. I have no idea how this kind of thing could occur... other than cell phones and a 5.4Ghz cordless phone, I don't believe I have any transmitting equipment in the house. The only possibility I can think of is a large cell phone antenna that is 100 yards from my house. Any thoughts or ideas on how to correct this problem?

TIA

P.S. My dslreports line quality test came back clean. Just two lost packets, one of each of the east and west coast tests.