QuickTime won't close.

QuickTime Player does not close after all windows of the app are closed and the app disapears from the dock.

Closing all open players does not automatically quit the QT Player application—you must actually use the "Quit" option. You can, of course, combine the closing of all open players and quit the application into a single operation by holding down the "Option" key as you select "Quit."

If I try to delete the movie I was watching it says that the file is being used and then I always have to force quit QT from the finder.

The QT Player does not "release" a file when a player window is closed. It only releases it when the QT app itself quits (or, in your case, is "forced" to quit). Until that time the Finder will continue to consider the file is "still in use."

Properly "quitting" the application should fix both of your problems. Also, be advised that opening the QT Player app does not autoimatically load a movie that was not already lodaded when the app was last quit without closing the movie player as opposed to double-clicking a movie to both open the app and load a movie to a player window for playback.

The thing is that other apps are still active and inmy dock even when I close the last window of this app, where with QT the icon disapears from the dock, thus I can not quit the app.

The application icon should not be disappearing and so this sounds like a Finder/system display problem. As to quitting, either try the "Command-Q" keyboard shortcut or double-click the app or a movie icon in the finder to restore and use the QT Player "Quit" menu. If neither of these work, it would tend to confirm that you have a system problem. I would normally check to see if you have the same problem using a different user account. If you don't have the same problem, I would restore the preference file to see it that fixes the problem. If you continue to have the same problem in both accounts, I would either replace the player app and recheck or reinstall the operating system.

I have to quit the app from the last window like you said witht the kyes and everything.

See above for further testing.

Before with Snow Leopard when I closed every window of an app the app stays open in the dock until I close it or it quited it self like iPhoto does.

Snow Leopard was working properly while your current system/software is not.

Do you know any other way I can twick the QT app into staying in the dock until I quit it and then to disapear?

There is nothing to tweak. Based on your updated description, your system is not working properly. This is not the way your system/this app should be behaving.

I had a similar Prob w quicktime 10.2 where no matter what I did all the files I have ever opened wouldn't close no matter what I tried. On a whim I decided to "clear Menu" on the recently opened files in QT's FIle menu and when I did, all the files closed that were opened. At least they no longer appeared above the QT icon in the doc nor when I 4 finger swiped down to show all open files in QT. very strange

Just press command+option+esc to open taskManager and select the program that you would like to force quit and press "force Quit".