I want to inform you that now, without any fixes, my search machine works with fragments without any bug, and in addition - without any "~", and in addition - in Cyrillic!
I only read you, but couldn't remember if I tested it with fragments of words, or not, and tested now.
I only wrote литера, which is the first part of the word литература - "literature". After 5 seconds there was found 51 topics, containing the whole word литература. The same happened with other words in Cyrillic. The same in Latin. I typed esse and received 5 messages Esse'x and essential. I haven't used "~" at all.
I'm sorry, but I cannot say that at me your "bug" exists. There is no bug with the fragments of words. May be you have to check your Windowses :))) I checked the problem with IE and even with Opera - no problem.