what does it say if you go to .osso/dictionaries (cd .osso/dictionaries) and then type "ls -la" whitout the "".. this should list whats in the directory.
Edit: Of course if the file isn't there, I suppose it's not reading the file. Just to rule out sillyness, you are infact using autocompletion?
I haven't messed with mine, is the file automaticly generated when using the feature?