I have a recurring problem with Blender 2.64: I import a model, I start to edit it then suddenly the precision decreases drastically so that I can't move anything where I want to (there are huge gaps between available positions.)

I think it's due to IEEE-754 floating point representation but how can I fix it?
(I didn't scale my model.)
EDIT: I just realized that when I move an something, the edit bar indicates:
D: 0.0000 (0.0000) global
D: 1.0000 (1.0000) global (with the example above)
So the picker may switched to integer...
