Hey Andy,
To help further, we'll need to know what version of V-ray you're using. Typically, this type of problem is due to displacement. But if you are not using displacement, then we'll need to take a look at your v-ray settings. Could you post screen shots of your V-ray settings? Also, if you havent' already done so, try restoring V-ray to default setting and see if you can get a normal render....its real easy to go overboard on the settings and you don't need to tweak the defaults much to get a good render. (before you ask how to restore defaults(or any other questions), please state vray version)
Sorry for the late reply......darn deadlines...