iTunes won't quit.

Macbook Pro, version 10.8.3

iTunes 11.0.2

Whenever I quit my iTunes from the dock... it just re-opens.

There is an iTunes update available 11.0.3 ... but when it's installing it asks me to close iTunes. I do.. but just reopens again. I have tried Force Quit and it also just reopens. I can't install this new version because the old one won't remain closed.

Any suggestions will be much appreciated.

Thanks!