hi Bosek, thanks for providing a crash report id. we have seen quite a number of similar reports about this issue in the last hours and this issue is likely caused by your symantec security software that is hooking into firefox (probably through a program/signature update done by them). other users reported that updating firefox in this situation helped with the crashes. you can download & install the latest firefox from https://download.mozilla.org/?product=firefox-48.0.2-sha1&os=win&lang=pl (polish version)