Hhmmm... keep on getting 500 Error messages whenever the VOI tries to rebuild itself. This sucks.
Update: Problem looks to be resolved.
Solution: Goto HTMLPerms in mt.cfg and uncomment it so that it reads: "HTMLPerms 0777"
Thanks shelley for the help!
Update 2: Problem still persisting in an intermittent manner. Weird. One moment it works, the next it doesn't!!! HELP!
Update 3: Problem is definitely intermittent in nature. Have contacted my webhost. They didn't change anything either on the server configs. Oh dear. I've got a problem.