[dba-Tech] curious mouse behaviour on laptop

Environment Dell Inspiron laptop. HP USB Optical mouse attached.

Suddenly all the right-button clicks are failing in all programs. I still
have the touchpad to get around this, but it pisses me off nonetheless. The
other mouse functions (left button and wheel) work perfectly; only the
right button's functionality seems to have gone away. Everything was fine
until about a week ago.

Why would this suddenly happen? My first guess was batteries, but given
that 2 out of 3 continue to work perfectly, that doesn't make obvious sense

Mice are cheap so it's not that big a deal, but being the
ever-so-eco-sensitive guy, I don't want to chuck this mouse into the
dustbin without at least an attempt to figure out what's gone wrong.
Reboots don't solve the problem, and neither does unplugging/replugging.

Any suggestions?

-- 
Arthur