I've bought and downloaded Neverwinter Nights Diamond edition and installed it under Wine in Ubuntu 12.04 lts.

When I play the game it seems to run perfectly except I can't seen the character or NPC's only their shadow.

I have looked for a solution on a web search but all the help to deal with this problem is no longer available.

I am grateful for any help I can get;
Stephen

Linux is not officially supported so GOG probably can't help you.

Try posting in the Neverwinter Nights section and see if anyone knows about the problem. You can find specific game forums by clicking on "community" at the top and scrolling down the list.

Might also try the Bioware Social Network forums, a lot of NWN players still hang out there I believe. If there's another, stronger NWN community I don't know where it is. Someone else might.

I seem to remember there being a Linux client for this game, perhaps that would be a solution?

I had the very same problem under windows. To solve it I had to turn enviroment mapping on creatures off.
Video options->advanced->disable Enviroment Mapping on Creatures, and see if it helps.

I was able to recreate the problem just 2 minutes ago for a test (win7). I turned Enviroment Mapping on Creatures on, and all the NPCs disappeared, except their shadows. I turned it off, and the NPCs reappeared immediately.

Just checked my non-Gog version & it doesn't seem to have this issue, I use win 7

There is, but it requires fiddling about to install the thing, since the installer looks for the original discs. Arch Linux has an AUR package that uses the Linux binaries/patchez to install the GOG version, but I am currently not in a position to translate that into manual instructions for Ubuntu (not at home, and with only my phone at hand).

That's too bad, I think I read about the client on these forums back when NWN was released.
But MadyNora's solution sounds promising, makes me think it's a driver/videocard issue.

Which graphics card are you using? On an AMD when I load The Legend of Grimrock the menu will be black depending on whether I have "use application settings" checked or not. So let us know if you've tried to adjust any settings first.

My GOG version doesn't either.

Have you tried this: http://www.gog.com/forum/neverwinter_nights_series/linux_playability ?