LHC will start in November, they're cooling now
http://press.web.cern.ch/press/PressReleases/Releases2009/PR13.09E.html
Mostly money - it was going to be hugely expensive and the Scientists didn't make a
good enough case about the need for it. The LHC has always been themed around the
Higgs Boson which gives it a strong story that politicians can understand. The SSC in
comparison appears a case of building bigger for the sake of it (regardless of whether
that is true)
Remember too that the Americans had also been up to their necks in the rising costs of
the ISS