You're not the only one. I have a 5000F myself that's useless under linux. I've been waiting a year and a half and there hasn't even been a glimmer of hope for support. The only thing I could find was this page a while back from someone with the same problem. http://www.freedos.org/jhall/canon5000/
Apparently Canon just doesn't think it's worthwhile to give Linux users any support, so not only are there no drivers but there's also not enough info for people to create unofficial ones.
I've been wondering if it's possible to set up a Win98 session under Bochs or something so that I can run the native Windows drivers and software, but it's low on my priority list right now. I'm still just trying to learn my way around Linux and getting it working the way I want. Besides, I'm not even sure Bochs can run something like that.
It sure is frustrating. If I had known Canon wasn't supported, I would never have bought this scanner.