A similar question was resolved in this forum post on a wireless connection issue with their PS3. Here is the best answer:
what solved my problem was simply moving the cordless phone away from my ps3. Because it was blocking the wifi signal from reaching. For those of you skeptical about this go. I tried everything else unplugging the router disabling the wifi for a few minutes, restoring settings. All to no avail, than my friend tells me to move my cordless phone because it's blocking the wifi. At first I didn't believe him but tried it anyway. And tada it worked like a charm, so it helps to try every option than just assuming. There isn't a one size fits all solution.
If that doesn't resolve your issue, there was also a link to this PS3 manual page.