Howdy,
Well, first off, a note about Virtualmin’s support – Virtualmin only technically supports Ubuntu up to version 10.04, the latest LTS release. So 10.10 might work, but it’s also possible you could run into strange problems 
If you log into your server as root over SSH, and type this on the command line, what output do you receive:
/etc/init.d/apache2 restart
Do you see any errors? And Apache really is running after all that… it’s serving files and such for your websites?
-Eric