Are you focussed properly?
Take a photo, if you have the technology, and post it somewhere on the web, then link to here. Raoul has lots of experience of optical telescopes and can offer quick advice on any lens aberattions.
Remember that Venus is unusual in terms of size and brightness, so you might not see the same effect on other targets.
The moon is too big to see small "ghosts", and stars are generally too dim for a weak ghost to be visible.
Have you looked at any other planets? Jupiter would be a good comparison, if it's bright at the moment...