unable to enter "ę" Polish letter while using Polish programmer's keyboard in MultiTerm

Polish letters (Latin with diacritical marks) are normally accessed using the AltGr (right Alt) key with the corresponding Latin character key, ex.: AltGr+a makes ą, AltGr+z make ż, AltGr+o makes ó, Shift+AltGr+l makes Ł. That is using the "Polish programmer's keyboard", which is widely used by Polish speaking computer users. That works fine for the following letters: ą,Ą, ć,Ć, ł,Ł, ó,Ó, ś,Ś, Ź (AltGr+X, Ż,ż, but does not work for ź (AltGr+x) as well as does not work for Ę (AltGr+E) and ę (AltGr+e). All the mentioned three combination has a function assigned (AltGr+x starts "Export setting" dialogue, while both AltGr+e and AltGr+E mark the field. I use version of the MultiTerm and all the combinations of these letters and Alt has been deleted from Options-> Keyboard shortcuts. Is there any other place to switch off the keyboard shortcut? Is it a matter of setting or simply a bug? That limits the usability of the MT. The same happens while editing a term in the Termbase Viewer of the Studio ( I work on Windows 2010.