Lately I've been having trouble keeping a connection to wifi, first at home and now at work. What happens is that after a while I'll notice that my phone is using 3G.

If I go into my wifi settings, I'll see a strong signal from my router. When I try to connect manually, I often get the message, "Failed to connect to network" with no further details. (There's a special place in hell for those who write error messages that give no indication of the nature of the people.) Other times I can connect, but the signal is reported as weak and drops quickly.

My computers can connect with no problems and report strong wireless signals. My roommates have no similar problems.

I have a Galaxy Nexus running Jelly Bean. My roommates have a Galaxy Note and a Galaxy S2, respectively, both on ICS.

What's wrong with my phone?

Additional details: My phone is rooted but running the stock ROM. I first noticed this problem while using Tasker to implement a Bluetooth wireless leash. I've stopped using the leash--and Bluetooth entirely--but the problem persists.