I had a bit of a strange issue with FireFox and Kde 4.7 on Kubuntu 11.X.
After downloading a file with Firefox, on the Dowloads Firefox windows, right clicking the downloaded file for the Open Download Directory action, instead of opening the Dolphin File Manager, it opened the KdeSVN application… Very, very annoying.
To solve this you need to reconfigure KDE, probably due to the fact that KDESvn was installed:
1) Goto System Settings
2) Select Default Applications
3) Select FileManagers
4) Deselect and select Dolphin
6) Restart Firefox
It should work now.