Chris, I'm surprised that this new 4500 with v1.15 loaded is having the same issues. Seems that having 2 of the same 4500s having different FW versions and now the new one exhibits the reboot issue. This would make me feel that there is something else up the lines that is causing this reboot or possibly a configuration issue.
What ISP service are you using? DSL or Cable? If you have DSL. I have worked with my buddy in OK that has a 4500 and had several issues with his DSL. Look for ATT DSL posting from me in this forum about his history. Turn out it wasn't the 4500.
If cable. Can you let us know how this unit is set up and what is all connected? including DSL/Cable modems, switches and other devices connected. What HW version is this new 4500? A1 or A2? What kinda of configurations have you done and changed?
Please let me know if you have reviewed the Gaming and GameFuel stick I posted. This works well for most people and have had good luck with this testings for Gaming and general internet use. Disregard the Gaming section if you don't game on PC or Consoles. I have to re-edit that for PCs and not consoles. Let us know if we can help.
DGL-4500 Gaming and Gamefuel for XBL