FRITZ!Box 7390 “looses” substantial amounts of time during 24 hours

My 7390’s firmware version is this: 84.04.85-18065.

There are other issues with the 7390 as well, but it’s a solid piece of router / wifi access point / pbx / dect access point / … – I do love my 7390, and I don’t want to swap it for anything else.

I didn’t experience those firewall attacks again, that I mentioned earlier.

But the box rebooted all off a sudden recently w/o leaving any reasonable or informative message.

Update re lost time:
Changing the NTP server (e.g. to 2.de.pool.ntp.org) seems to help.

Update 2011-01-05 re lost time:
No, changing the NTP server did not really help at all. I am losing about half an hour quite often. The NTP server is now again set to de.pool.ntp.org.
Manually re-connecting the Internet connection under Internet / Online-Monitor helps, if you want to get the time corrected instantly.
But I don’t want to imagine, I oversleep a train connection, because my FRITZ!Box initiated alarms on the phones do not occur at the right time.