I don't know it was, but later my additional mouse buttons started to perform action "Play Next/Prev Sound track", and when system was fine this buttons used to send me to prev/next page in the Internet Browser or in File manager. So, I just recovered my system from backup and it works fine. But what's happened with system is still a mystery for me...
Originally Posted by anishakaul
What options do you get when you right click the applet ?
Delete from Panel
Attach to Panel
But it is now, and what was when I had bug - I can't say exactly, but it seems to me that options were just the same