Keyboard Layout Changes

I write document in english and spanish, so I have to use the US and the US-International keyboard layout. I have the keyboard bar active and use it to change layouts. The problem is the keyboard layout changes "by himself" constantly. I thought this was attached to the program I'm using, or the document, but it's not.

For example, I'm writing a WinWord 2007 document using the Intl layout, and using accents and everything. Suddenly, I try to use another accent or symbol, and it doesn't work. If I check the language bar, it changed to US Standard layout. I disabled the shortcuts to change layouts, so this is not the problem (I mean, accidentally hitting the shortcut...)