Easiest fix: install USB Overdrive or SteerMouse.

LCC sucks. Don't waste your time with that junk.

I am all for using USB Overdrive in place of LCC. While the LCC interface and feature set is nice, it has proven to be extremely buggy over the years. And it's not the same old bugs. Each new version seems to introduce another one.

However, USB Overdrive is not free and I don't think that people who just shelled out hard-earned money for a fancy mouse should have to pay extra for drivers that work right.

Logitech should just license USB Overdrive and ship that as the Mac drivers for their mice, because LCC seems like it will never be "fixed." They've had years to get it right, and just can't do it.

An even better solution would be if Apple's Mouse prefpane in System Preferences would allow configuration of multi-button mice. Seriously, in 2010, that seems like something we should just expect from a modern OS. Now if you buy a Apple-branded mouse, the Mouse prefpane suddenly *does* get all the configuration options you could ever want. I guess giving us all those options with a $5 off-the-shelf USB mouse would cut into Apple's peripheral sales...