Clutch problems

I have a major problem, have had problems with clutch slipage in the past, caused by chain lube build up on the rod. Went to ride the Bike yesterday. clutch felt funny after taking off, clutch hydraulic lock at clutch lever and bike stoped moving. I pulled clutch slave from the bike and it still will not engage. Opened up the case and ever thing looks OK. Oil has no burned smell and clutch plates are in specs.Can't under stand how it can work one day and not the next.