Reboots early morning? Just started? Summer only? Is your power supply regulated?
Here is an unregulated 12V 1A wall wart powering a RB433AH.
Daily voltage report for test on sep/01/2012
23:00 = 15.3 Line voltage = 130
22:00 = 15.2 Line voltage = 129
21:00 = 14.7 Line voltage = 124
20:00 = 14.5 Line voltage = 123
19:00 = 14.5 Line voltage = 123
18:00 = 14.5 Line voltage = 123
17:00 = 14.0 Line voltage = 119
16:00 = 13.7 Line voltage = 116
15:00 = 14.3 Line voltage = 121
14:00 = 14.1 Line voltage = 119
13:00 = 14.2 Line voltage = 120
12:00 = 14.2 Line voltage = 120
11:00 = 14.3 Line voltage = 121
10:00 = 14.5 Line voltage = 123
09:00 = 14.6 Line voltage = 124
08:00 = 14.6 Line voltage = 124
07:00 = 15.2 Line voltage = 129
06:00 = 15.3 Line voltage = 130
05:00 = 15.0 Line voltage = 127
04:00 = 15.8 Line voltage = 134
03:00 = 15.8 Line voltage = 134
02:00 = 15.6 Line voltage = 132
01:00 = 15.7 Line voltage = 133
00:00 = 15.4 Line voltage = 130
Since voltmonitor started on 09:00:10 aug/30/2012
Maximum = 15.8v at 03:00:10 sep/01/2012
Minimum = 13.7v at 16:00:10 sep/01/2012
If you used a 24v unregulated supply, the d.c. readings would be twice that. At 30 volts, that router power supply will shut down until the voltage drops below 30 volts. Note what happens to my voltage input between 7am and 8am. Twice that would be passing 30 volts going down.
Just a thought...