.desktop file has no 'Type=' entry

[Martin Airs]

good day all,

I'm currently using KDE 4.5.95(RC2)
I don't know when it happens or why, but after a while when I click an application icon in my panel to start for example firefox, i get a window popup saying...

The desktop entry file /usr/share/applications/mozilla-firefox.desktop has no Type=... entry

and the app doesn't start.
when i first start kde everything is fine, and then I could go out for an hour or so, then when i get back this happens, I don't know when it starts happening.

to fix it i can just kill and restart plasma-desktop and this will sort it out, but after an unknown period of time, it will happen again

this has been like this for the last couple of releases also.
I wonder if anyone else experiences this and how it can fixed

Thanks
Martin