I dunno if the story is true but I'd heard that they had someone in Australia who was gonna finance it which turned out to be some kind of hoax and basically they can't find anyone to finance it..
A Red Dwarf movie would be cool if they stuck to the style of the show. The last couple series, especially 8, sucked on the writing front so I think they would need to sort that and I can't help but feel they would compromise the quirkiness and style of the humour/sci-fi to try and make something more action orientated, more 'hollywood'.. I quite liked the idea of kinda doing a 'Begins' thing and not continuing from the end of series 8 though.
But like Black_dust said, Craig Charles has been caught doing drugs and they are having problems getting it together so it's gonna be a while off yet...