Razr..3g and Signal Drop

[Erin30Ga]

Hey...I just upgraded to a Razr from a thunderbolt...when I use the hotspot or usb tether after a few mins my 3g drops and a red x over my signal bars..so i unplug it..wait about 5 mins and everything comes back.I dont get it...never had this problem with my thunderbolt..I could tether for days on that thing.Any help??? Thanks