My iPad 2 can't load new Yahoo emails from my home WiFi (but loads them fine in other WiFi environments and loads Gmail messages fines at home)

My iPad 2 had no problems loading e-mails until about a month ago. Then it started periodically being unable to load new e-mails from one of my two Yahoo accounts (the primary one), but the secondary Yahoo account worked fine. (It says "Checking for mail..." and never stops checking). This only happens when I'm at home, using my home WiFi (a slow connection.) Now, for the past two weeks, about 95% of the time, neither of my Yahoo accounts works on the iPad, although I have no problem accessing these accounts on my iPod Touches or on my desktop Mac mini. If I take the iPad to my neighbor's house and use her WiFi, I can get the Yahoo mail. (She has cable/internet through Comcast; I have DSL.) I can access the Yahoo mail in public WiFi environments like Starbucks, Barnes & Noble, and the Apple store. I upgraded the operating system to ios 6.0.1, and the problem didn't go away. I've been to two Apple stores and seen two different "Geniuses" about this. The first one observed that although the iPad could load mail while in the store, it was doing so very, very slowly. She did a complete restore (erasing all of my apps, photos, etc.) but when I got back home, the problem resumed. The second Genius couldn't figure the problem out, either. He suggested I contact Yahoo, which I highly doubt will get me anywhere. I eventually added back all of my old apps, but then deleted them again in the past few days thinking that perhaps a persnickety app was causing a problem. No luck.