When I enable the "Disable all menu access keys" option in xfce4-terminal I am still able so switch between tabs using alt+(some number). This causes the terminal to intercept the key combination which interferes with some terminal applications (irssi in particular).
I've verified that this bug came in to existence with the 0.6.2 release, It is not present in 0.6.1 or 0.6.0
From what I see from digging around in the 0.6.1 and 0.6.2 code, it looks like that menu option disables mnemonics. With mnemonics disabled, you'd no longer be able to press alt+f to access the menu with an underlined f (or use any alt+x shortcut to activate any menu action). It seems like alt+N (to switch to tab N) being disabled was an unintended side-effect. I don't see any relevant changes in the Terminal code though. This change likely happened in the gtk libraries. In the preferences panel, this option is under "Menubar Access". The documentation (http://docs.xfce.org/apps/terminal/preferences) doesn't mention anything about disabling alt+N shortcuts for tab switching. There's a FAQ (http://docs.xfce.org/faq#editable_menu_accelerators) that gives instructions for changing/removing key bindings. I could be wrong, but I'd guess that it was the 0.6.1 and earlier behavior that was the bug, not the 0.6.2 behavior.
Thank you for the detailed reply. I removed the shortcuts per the docs that you linked and everything is working perfectly. Thanks again for making a rockass DE.
Expanded the docs to explain the difference between mnemonics and accelerators. http://docs.xfce.org/apps/terminal/preferences?&#menubar_access