Andrzej Tomaszewski wrote:
Even stranger is for me the fact, that on my laptop LyX looks like on the .png above (some Polish letters are displayed and some other not), but on my desktop none of the diacritical marks looks incorrectly apart from ó, which appears in Western European charset.
Did you set the language for non-Unicode programs correctly in "Control Panel" > "Regional and Language Options" > "Advanced"?
Joost