Program Auto Hiding? HELP!

Hi, this has been going on for a few days now and it is REALLY annoying. I have tried everything. It is hard to explain, but for example, when you have iTunes open, and you click on safari, it hides iTunes and opens Safari, then when I click back to iTunes, it hides Safari.
I think it is something to do with the Alt key, because when I hold that down and switch application, it keeps them both open.
But it is only happening on one login on my iMac. If I log in as a different user, there is no problem at all. Is it in settings?

Thanks in advance,
Dan

Well that's certainly strange, because holding down the alt key actually hides the application. Please double check what you are doing when the problem happens.