Thank You ccfj1 for the answer. The problem is that I used navtweak2.7 for a month in Win7 and WinXP without any problems, but now it crashes. It crashes even if I only open navboot file and then try to save it without any changes. I don't know what to do to work with my custom navi project. Until now I managed to change the sky, splash screen and put cyrillic alphabet in Fonts and want to try translate Lng_Detsch.txt in my language, but with this bug I don't know how to do that.