When I make a change in the KDE menu editor and then save the following message comes up:

"Could not write to /home/user/.config/menus/applications-kmenuedit.menu"

There is no such path so I made a path and file and the same results. I'm using Arch Linux and KDE 4.6.5.

This is extremely odd. I gather your username is "user" in this case, with a home directory of "/home/user/"?

You may want to try rebuilding the Sycoca (kbuildsycoca4 --noincremental) and ensuring that "applications-kmenuedit.menu" doesn't exist elsewhere under ~/.

I was having the same issue for a while and stumbled on this post looking for answers. The rebuild Sycoca command didn't work for me initially, but I solved my problem by deleting the contents of /var/tmp and running the command again. I'm not really sure if it's a great idea to empty that directory (fairly new to linux) but I haven't had any issues and the menu editor is now working fine. Hope this helps someone else.

The contents of /var/tmp will persist across reboots, but are not to be used for data which is essential to the application - ie. caches, etc.

As such, it was safe to delete it's contents.

Thank you for your comments bcooksley and floater.

Good news, I just reinstalled my Arch system and it works fine OTB.

I'm so happy with the progress KDE is making. Just keeps getting better and better.