G604T firmwear

Hi.
I have a D-Link G604T ADSL wireless rooter. I can't seem to get the
firmwear to upgrade. Has anyone got this rooter and had similar problems?

If I go into the management browser, and go to the update gateway section, I
can select the firmwear file using the browse feature, and then click
update. A message at the bottom of the screen says that it's updating, but
then, after a while, I just get the 'page cannot be displayed screen'.
That's it, no further progress. If I try and log back into the management
browser, I just get the same 'cannot be displayed' screen. The only way I
can get the connection back is to remove power from the rooter for a while
and then press the factory restore button on the rooter itself.

I've disabled all firewalls, antivirus etc but it just won't work. The only
thing I can think of is that the firmwear updates are not cumulative, and
that therefore I must have missed one I should have got, inbetween my
current one and the one I'm trying to install.

Help?