For solving random reboot and dialing reboot in my D2G, I tried flash different ROM and SBF, but can not get rid of it.
When I tested the airplane mode, I found it will not reboot anymore, but I turn on the mobile network, it was rebooted.
So I thought is it because of the CPU can not supplier enought power.
For this thinking, I downloaded the setcpu app. to test my phone.
The D2G works on the CPU frequency from 300 to 1200Mhz, so I modified the 300 to 600 and 1200 to 1000. By the way, my phone rooted.
After all above, my phone has 24 hours no reboot whatever standby or dialing.
Hope this can help the other people who has the reboot issue.