Phone call quality suddenly choppy, even though signal is good

I have a Sprint HTC EVO 4G running the Fresh Gingerbread ROM. The call quality in my apartment has always been great. However, this week the call quality has been extremely choppy to the point of not being usable, no matter how I hold it. I haven't really done anything to the phone or my apartment, even though all its signal bars except one are full. If I remember correctly I still have good call quality at work, so I don't think its solely a phone issue... Any idea what's going on?