I have a nearly identical setup as you do, and my Hi-port has worked flawlessly since day one. My setup is Comcast cable modem(Linksys CM100)->WiFi router(Linksys 610N)->Hi-port. I used all the defaults on the setup disk that came with the Hi-port. My Hi-port is set to Router on the advanced routing config page, not Bridge, so you may want to try changing that.
You may also want to double check your connections. If the blue light is on and you don't get a dial tone, you may be connected to the wrong phone jack. You may have accidentally put your sim card into the second sim card slot, so your dial tone would be on Phone line jack #2. Good luck.