How can I fix the Wi-Fi button or prevent Wi-Fi errors when turning it off and back on?
I've had the same thing happen to me on my LG G2X running CyanogenMod. So I don't think it's related to your specific device or software. Moderate success has been reported using the "FXR WiFi Fix And Rescue" app, and it's been tested on the Vibrant. You can also try WiFi Fixer.