*My* interpretation

Rating: Null/10 (20 May 2004)

*Spoil*
I agree mostly on the dream theory but I'd like to add that the bum behind Twinkie's is behind it all. He has the mystical box which contains the beast(s?) which either a)kills people b)messes with their heads or c)both. Those two old people are also somehow related to him or his cube (they come out of his paper bag). There was also this random guy who said he had seen a dream about the bum (possibly similar to Betty/Diane's dream) and then has a heart attack while investigating.
The rest of the loose ends can be explained by saying they were meant to be a part of the TV series but in the movie there was no time to tie a knot. Therefore Lynch got this "let's f*ck up some minds with a blue cube"-idea and inserted a few shots that appear to be random here and there, throughout the movie. These are supposed to form the core of the plot and they are beautiful: they either add mysteriousness, surrealism and weird collocations to old movies/series or generally f*ck with your head. These weird shots are the essence of this movie and make it truly a David Lynch film.
I'd give this movie 8½ out of ten. It's not as weird as Lost Highway and there's more room for speculation. That's why I actually liked it.