michaaa62, I have performed the first part and successfully updated libqt4-core. The phone worked at first, but I got errors pretty soon after, so I restarted it and now it seems it is in infinite boot cycle.

As far as I understand, now I should:
1. Install flasher-3.5
2. Follow these steps to get it working on 64bit Win7.
3. Run flasher-3.5.exe -F RX-51_2009SE_20.2010.36-2_PR_COMBINED_MR0_ARM.bin -f -R

Please correct me if I'm wrong. Also, if my battery is not full (but as far as I remember over 50%), should I do it?