Mouse setting in system preferences

Could the Kensington Works software be interfering with the mouse speed.

Can you run the mouse without the Works software.

Could be a corrupt preferences file.

Click once on your Desktop, click on Go in the menubar, then select Go To Folder.

Enter this text.

~/Library/Preferences/com.apple.systempreferences.com

press Go.

A new finder window will open with that file highlighted, move it to the Trash.

Restart your mac, the file will be regenerated, when your mac has started up

change the mouse track speed in System Preferences> Mouse.

Restart again and see if the mac has remembered your mouse tracking speed.

If this has worked then you can empty the Trash of the original file.

When you look inside the Preferences folder have a look at the list of different

preference files and check that there are none with, random alphanumeric characters

after the .plist extension. If you find some these are indicators of corrupt files

you can put them in the Trash and empty the Trash. Then restart your mac.