There was a similar thread here some time ago but I have failed to find it.
There was a suggested cure which involved sitting in a swivel chair with your head well over to one side. Continuous rotation of the chair (get someone to rotate it for you) will make you feel awful and you may well be sick. However, it was claimed that this would build up your tolerance and was recommended for military pilots who were having this problem during training.
I can't vouch for it personally though. If you do find a cure which works for you, please let us know.