With cyrillic symbols in eng_stringtable game even dont start.
If you put them on the first, line, probably. This is a known issue with any non-latin characters on the first line, which seem to be read in a way that makes it die on any fancy character sets. This is easily avoided by not puting anything fancy on the first line.
For the rest of the file, that's probably not the case, as you've posted a screenshot with (buggy) cryllic characters in it, so they can be read and displayed. There might be a conicidental problem that's causing a weird crash from your edits, but my guess is that it's the first line issue...