Great, it did solved the issue.
The procedure I did was that I first went and deleted font cache file, then I updated koreader with latest nightly (or, at least the same as in the first post, if there's a new nightly, didn't checked).
After I started koreader, everything works fine.
I now think I should have try to do a bit different procedure, ie: first update and try to run it, in case that stable version somehow fixed corrupted font cache file.
But, all in all, it was corrupted font cache file. It's good to know. It also might help to know why nightly crashed, but stable version just loaded fine.
Thanks jonnyl, a bit of karma is sent your way.
