Some of the filters only work on 8 bits/channel images (something I've been prodding Adobe to fix for a loooong time).
Assuming you're not trying to preserve high accuracy high bit-depth information, you can do Image - Mode - 8 bits/channel to get your document into condition to work with those filters.
Noel, thank you SO much. I figured it had to be something simple, but Adobe wouldn't even talk to me unless I purchased CS-6. Really appreciate!
Yes, Noel is great, and also very quick.
The Bit-Depth issue is one that has been tripping up PS users, since 16-bit support was added in about CS. With many Images (8-bit), things worked, just like in earlier versions of PS, then suddenly, some Images would NOT allow the use of some Filters. Now, with even greater Bit-Depth, people are still running afoul of that limitation in some Filters.
Like Noel, I would like to see some Filters re-written, but maybe it's a bigger deal, than I think it is (Noel would actually know).
Good luck, and if he's hit the cause, you might want to read over this article: http://forums.adobe.com/thread/1058744?tstart=0
Thank you, Bill, that's nice of you to say.
Chances are it's a bigger deal than it would seem to most folks to rewrite these old filters because of the legacy of Photoshop development BUT...
Isn't that why we pay the big bucks for this software? For goodness sake, the application costs 3 times as much as the entire operating system (even more than that if you're a Mac user).
Adobe claims they need to see specific justification from users but that's nothing more than a cop-out. Any reasonable user EXPECTS the features to work in every sensible bit depth. The very existence of threads such as this one proves it.
C'mon Adobe, you can't just keep writing new features and never finish the old ones. You make gigabucks from this software! You can spare a few hundred thousand for a couple of guys to sweep through all the old filters. Hey, send some $$$ my way, I'll be more than happy to do it for you!