? marks coming from reverse geocoded response
Considering the presence of the dash with the question marks, it seems exceedingly likely that this is a character set issue and not a case of Google sending back question marks. (How certain are you that your site is specifying UTF-8 as its charset?) If you don't care about internationalization, then you can work around the problem by forcing the results into English with the language parameter in the URL (see below). This is, of course, not ideal, but may be acceptable for some uses.
In the likely event that the above workaround is not acceptable, try running your code with the results from http://maps.googleapis.com/maps/api/geocode/json?latlng=60.0486851,30.3197483&sensor=true&language=ru (note the language parameter tacked on to the end to force it to return Russian-language data) on various browsers to see if you can replicate the question-mark problem. (If you know what browser/platform the user was using when they experienced the problem, all the better.)
Maybe the person's response was returned content in Cyrillic or some other language and your charset is not the proper one?