That will actually be in the core files – plugins/buddypress/bp-core.php, buddypress/bp-groups/bp-groups-templatetags.php, and the same for forums. This is a great example of why you shouldn’t mess with core files (and why I’m a fool for doing so), but it’s probably not your problem at all. I think most people’s problems are stemming from other plugin’s or the theme loading another version of jquery. I’d check the source code from the offending pages and see if any other jquery libraries are being loaded.
