"Authentication failed" when trying to upgrade from 10.04 to 10.10

I get the following error message when trying a network upgrade from 10.04 to 10.10:

authentication failed. authenticating the upgrade failed. there may be
a problem with the network or with the server

I googled that error and found one proposed solution:

gpg --keyserver keyserver.ubuntu.com --recv 437D05B5

gpg --export --armor 437D05B5 | apt-key add -

However, this seems to have screwed up at least one guy's system.

Is there any safer way of solving this (besides doing a fresh install)?

I did not solve this directly, but found a workaround: I put the latest Ubuntu (11.10) on a USB stick, booted to USB, and selected 'upgrade Ubuntu' from the options. Worked fine.