How can i fix my table saw: Performance FMTC1500TK?

My Perfomance FMTC1500TK was working fine but now, whenever i try switching it on the blade begins to turn but then trips the fuse on the mains board after about a second. The blade turns freely when unplugged and the fact the blade begins to turn when switching on would tell me the belt in ok.
Although bought from B&Q a few years ago it has had little use since.
Any ideas would be appreciated.