I believe I have found some issues which seem to be the cause of a couple of crashes.
1: First launches of Kdenlive works fine and you select your default project type, etc. Subsequent launches will kill X completely. Deleting the /home/.kde/share/config/kdenliverc file stops the crash (as many have reported) until you close kdenlive agai whereupon it will crash on next launch. After some testing, I have found that the solution appears to be an error in the kdenliverc file, in particular the line which contains the version number. Line 58 says "Version=0.0.5". When changed to read "Version=0.6", the program opens like a charm. Upon cleaning exiting Kdenlive, this file is overwritten with the incorrect version and the program won't load until the version line is changed back to "Version=0.6" again.
2: I personally have had an issue where Kdenlive will crash upon opening a previously saved project. The solution seems to be the last position of the timeline cursor when exiting the program. Line 3 of the kdenlive project file reads:
If the variable "timeline_position" is set to anything other than 0, the project will crash upon opening. Editing a broken project file and changing this variable to "0" again will repair the project and allow it to open.
I hope this information is useful to someone, and of course, that the issues are fixed. At least now I can use these workarounds to actually edit some video instead of being frustrated.
Thanks for the great application.