Ok I did more research on the E4200 and a firmware update may fix this issue.
Release Date: June 25, 2012
Firmware version: v2.1.38 (Build 138143 )
Changes:
- Added Cisco Cloud services
- Added support for Class B and C subnets
- Updated WiFi driver
- Fixed guest network setup issue when router LAN IP set to 192.168.3.1
- Removed "Restore Previous Firmware" button
- Fixed some minor issues