Roy, I think you have three problems: shutter speed, shutter speed, and shutter speed. I forget what camera you have .. no, by looking at your EXIF I see it's a 350D. As I understand it, the 350D sensor is similar to those in my 20Ds: in other words, you have plenty of room to increase your shutter speeds up by increasing your ISO. With my Canon 100-400 and 500 f/4, I use these numbers as a rough guide:
100 ISO: have never, ever used it with these lenses
200 ISO: use only when the light is really, really bright (e.g., I'm getting something like a 4000th or a 6000th at ISO 400). (Depends on desired depth of field also: sometimes I'd rather shoot wide open and drop the ISO because I want to blur the background.)
400 ISO: Use this unless there is a good reason to use something else. Around 80-90% of my 400 and 500mm shots are at ISO 400
800 ISO: don't be afraid to go to 800 if you need it. If I am getting less than about a 750th on my image stabilised lenses, I go to 800. Slip over to Bird Forum and have a look at my Australian Owlet-Nightjar -
http://www.birdforum.net/pp_gallery/...cat/500/page/1 -which was taken in dying light at 800. Notice that what blur there is is depth of field, not motion. I took other shots of the same bird in the same light at 400 ISO and a 350th instead of a 750th, but the 800 ISO shots are clearly the best ones.
1600 ISO: Use it if pushed to it. 800 is better if you can.
Remember that I'm talking about image stabilised lenses here: with the 400 f/5.6 you should probably be using even higher ISOs than I use. Shutter speed is king.
With my 100-400 I like to stop down a half-stop to f/6.7 as routine to improve the optics (but open it up if need be), with the 500 prime I don't bother: it is superb even wide open, so I use it that way. I've never used a 400 f/5.6 but everything I have read about it says that it's just like my 500 - every bit as good wide open as it is at f/8.
Hope this helps!