When setting keyboard shortcuts from the preferences, any "Alt" event detects as "Meta+Alt", I use a US keyboard layout and have no special edits to the configuration.

if I quit QtCreator and edit the QtCreator.ini file to remove "Meta+" from the string, then reload QtCreator, The key binding works as expected.

This problems happens in both OpenBox and KDE4.

— Pressing and releasing the alt-ket from XEV

KeyPress event, serial 48, synthetic NO, window 0x2000001,
root 0x287, subw 0x0, time 9754850, (104,77), root:(3623,1003),
state 0x10, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False

KeyRelease event, serial 48, synthetic NO, window 0x2000001,
root 0x287, subw 0x0, time 9754882, (104,77), root:(3623,1003),
state 0x18, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False