My 3G / Wireless signal cuts out when the phone sleeps.
Check that your devices Power Saving options are disabled from the main Android Settings menu. When some phones go to sleep with power saving enabled, switching is prevented between 3G and Wireless connections.
Ensure 'Keep Wi-Fi on during phone sleep' is set to the default of 'Always'. Locate this option in the Settings menu of the BuyItNow Catcher application or find it in your devices Wireless Advanced Settings menu.
Some HTC phones will turn 3G off between 00:00 - 07:00 regardless of preference. In the Play Store there is an application called SmartSync Disabler to fix this.