USR5461 losing dhcp every now and then

Dear all,

I have a U.S. Robotics Wireless MAXg Router (USR5461),
which is connected to my ADSL modem.
Usually, it works great. However, every few days I have
to reboot the USR5461.
It seems the DHCP server stops working.
(I say this, because I can still ssh to my work, but not
read my mail, use a browser).

Does this ring a bell to anyone?

Thanks,
Dan