Hi,
First of all, make sure you're using the latest firmware version (00.06.06.1).
Second, check your router local time and see if it's synchronized with a local time you're referring to, it might be that router is showing whole different time and reboots when it shouldn't suppose to.
If the issue still persists even after you checked everything - download troubleshoot file from System > Administration > Troubleshoot and click on Download button next to "Troubleshoot file".
EB.