Discussed many times already on the forum and of course, is due to the fact that IVAP uses the same hotkey as GSX (CTRL+F12) so it's normal that two addons can't use the same hotkey at the same time.
Of course, you can redefine the hotkey used within GSX using the "Change key assignment" menu under the "Couatl powered products" menu, and I believe it's also possible to change it from within the IVAP program, your choice which one to change, but they can't use the same key.