Matt Laur , Aug 17, 2008; 09:58 p.m.
I suppose it's not a question of what's reasonable, it's a question of the buyer's expectations and how you represented it in your description. Yes, an "actualtion" is a shutter release. Click.
I don't recall what the D300's shutter is rated by Nikon to suport ... 100,000 actuations? It's a young camera, and perhaps the buyer wasn't expecting it to be a fifth of the way through its likely life already.