Disabling Server Certificate Validation on Windows Mobile 5, 6.0 and 6.1
Some secure wireless networks use certificates to verify the identity of the devices on the network, including servers. In some cases this functionality may be unused, in which case you can usually disable certificate checking.
On most desktop computers disabling certificate checking is as simple as ticking a box, but this option is not displayed on Windows Mobile. However, the option does exist and can be enabled with a simple registry edit. This appears to work on Windows Mobile 5, 6.0 and 6.1. The option will apply to all wireless networks and may prevent you joining other secured networks.
You will need to install suitable registry editor to make this change. Open the registry editor and start by navigating to "HKLM\Comm\EAP\25". Create a new DWORD value called "ValidateServerCert" and set it to "0". In some cases a soft reset may be required for the change to take effect.