A clean re-installation of your OS would likely clear it but it seems like a lot of trouble for a virus that is just screwing with your DNS or Host file.

Sounds like you really just need a good anti-virus program. There is even the chance you purged the bug when you cleared your cache/s and all you need to do is repair the damage.

If and when you get the system clean you might consider installing something like Spybot Search & destroy and allow it to lock your host file and system settings.

combofix can fix a number of rootkits.

First run Security Task Manager.
Quarantine anything that looks suspicious (to you, not STM).

Then run CCleaner.
Best temp file and cache cleaner out there.
Also cleans up dead registry files and lets you access the startup menu.

Then run Spybot S&D.
I've had pretty good luck killing re-directors with this.

Lastly install and use Super Anti-Spyware.
This is the free version.

I <3 Linux. Good luck w/the rebuild!