I bought iPhone 5 last Novemember and had same wifi connection issues several times. The trick I learned from Apple Care support is:
1. close all applications run in background
2. hold top button and home button at same time for few seconds until phone screen become blank and then apple sign shown. (this is called hard re-setting)
By doing that, the issue is resolved.
I was told that we need to turn iPhone 5 off at least once a week. Just like keep computer on for too long, it will eventually eat your memeries. My son has iPhone 4, never had same problem. It could be iPhone 5 issue.
hi matt! i also have the same problem. i cant connect to new networks. maybe i enabled or disabled settings that lead me to this. please help. what access control that should not be enabled? hope to hear from you.