Windows mobile not connecting to wifi modem's internet

Hi friends, i have HTC touch running on windows mobile 6.1. I have my modem configured for a static ip configuration, and both my laptops are connecting to it via the static configuration where
IP is : 192.168.1.x
Subnet: 255.255.255.0
Default Gateway: 192.168.1.1
DNS Address: 192.168.1.1

Before on i used to easily connect to the wireless network with the same settings, but recently it connects for one second and then it seems as if my modem bars the mobile's ip from data exchange and it reamins connected to internet only for a few seconds. I reformatted the phone completely, but even then the same thing is happening. Can any one help me?