I've added the filter panel in Dolphin (4.6.2) however all the options are disabled (ghosted). Anyone know how I can enable them?

As far as I know you need to enable Strigi to use the filter options. See Desktop Search in System Settings.

probably Nepomuk (and maybe Strigi) needs to be enabled

And it needs to be enabled for the folder you are currently browsing.

Ok, Nepomuk is running but Strigi is not.

I went to Desktop Search in System Settings and checked the option to enable Strigi but soon realised that Strigi is not running (installed) on my system. I'll report back once I've got it installed etc.

I think I need a little more help here as there's not a lot of information out there on Strigi - unless you want to disable or un-install it!

I installed strigi-daemon but this had no effect, I rebooted just to be sure.

I installed strigi-client and similarly there has been no change, the Strigi service is still not running.

Any clues as to what else is needed e.g. is there some other package that is required or do I need to add something to startup?

did you enable Nepomuk and Strigi in systemsettings (the "desktop search" module)?

Yes, both are enabled - Nepomuk indicates "Nepomuk system is active" whereas Strigi says "Strigi service not running"

I found a post on the archlinux forum which suggested replacing the .kde4/share/apps/nepomuk folder with a clean one. One reboot later and Strigi is operational.

Filter options are now working.

While I'm glad this is resolved I can't help but think that it shouldn't be this complicated!