Forum Moderators: phranque
The reason that this happens is that the browser inherits many form objects from the OS. These seem to exist on an level (or z-index, as it were) above everything else on the document. Flash objects behave similarly.
I have yet to see a solution to this - but one may well exist and you are in the right place to get it! One solution I have seen used is to place the form objects on a layer which is set to hide when the drop down menu is triggered. Definitely not a graceful solution though!