It's fixed by itself guys... I don't know what happened. By the way flash tweak plugin didn't help me. I tried it either. I have libflashplayer.so v10.0.3 or smth like that from TexasInstruments. If you want to try it - give me your e-mail.
I don't know how it had happened.I had 2 files(original one and TI file), I tried both but nothing was going on. Than I just renamed TI file to libflashplayerTI.so, so maemo system cannot recognize it as a default and set standard one, libflashplayer.so from original. I remember I launched several apps(home tutorial applet, which requires flash player and tangram game). After I didn't touch the phone for 7-8 hours. And...miracle! I'm able to watch flash videos in preinstalled browser!