Save Failed. Error parsing XML stream

Hello.When trying to save XML form from file search results, or just trying to replace some text using search options I get the following exception:

com.ibm.designer.domino.ide.resources.NsfException

Details:

Save failed

Error parsing XML stream.

Another error, when I’m trying to save XML file(different form) editor returns:

"Save could not be completed.

Some charachters cannot be mapped using CP1251.

Either change the encoding or remove a characters which are not supported."

I have no idea which charactes it could be, I’m trying to change encoding via preferences → speling. But when I press apply button nothing happens, seems like editor doesn’t perform any work. And, yes I get the same message about encoding(with CP1251) having, for example UTF -8 in preferences.

Advanced search for DDE is very nice innovation but it seems a bit unfinished.

Does anyone have similar issues, any ideas how to handle or workaround them?