Q: Suddently I cannot use the functions of my magic mouse

Hi PietralataKK,

I understand your mouse was working fine but now you have lost the multitouch features of the mouse.  You don't mention if you can click or move the cursor with it.

For this please start with this article to troubleshoot,

Desktop computers: Troubleshooting wireless keyboard and mouse issues in Mac OS X v10.5 - Apple Support

Then for the "trackpad" functionality check out,

Trackpad or Magic Trackpad is jumpy or erratic - Apple Support

Yes, it talks about Magic Trackpad, but the top of the Magic Mouse is like that.

Thank you for visiting Apple Support Communities.

Nubz