Wireless Mouse Problem

I am experiencing problems with my wireless mouse.  Periodically it
looses connection with the iMac; the cursor freezes, and I needed to
force the iMac to shut down by holding the on/off button down.  When
the computer restarts the mouse is functioning correctly.  Then later
on in the day the same freezing will likely occur again.

The battery icon bar indicates that the batteries are OK. I have used
the computer for several years and never had this problem before.

Can you suggest what might be causing the problem?  Are there any
diagnostics that I should run>

Thanks for our help