Losing modem connection with MBR900

[mikev]

I have a Sierra U301 modem in a MBR 900 router with Sprint Wimax (4G) service. Periodically the connection between the modem and router loses connection. My modem still has a connection light on it but the connection light on the router turns off. If I reboot the router, either by powering off or through the software or if I unplug the modem from the usb port and plug it back in I regain connection. There is no rhyme or reason when it does this. I am on my second router and both have had this issue. I have contacted Cradlepoint and they said to do an upgrade on the firmware for the router and modem, which I had been doing and did again with no improvement. Any thoughts on what might be causing this issue?

Thanks

[NickDBLG]

Hi,
Have you ever used the U301 without the router and did it used to do this? How good is your signal strength especially when you lose connection?