A recent commit to 2.4, e6fe7859446c6c8cc72769f5806255ed5fd309e9, updated the set of input event constants, which inadvertently changed the name reported to HAL of some input device pins. This commit went in to the 2.4.7 release.
Here's some discussion by Jeff Epler about the bug: http://emc.mah.priv.at/irc/%23emc-devel/2011-11-13.html
Here's Ed Nisley's blog post on the bug: http://softsolder.com/2011/11/13/emc2-logitech-gamepad-trigger-button-name-change/