Why isn't my Toyota Quilt 50 catching the bobbin thread?

My two year old machine has worked reasonably well and had quite heavy use. Yesterday, it developed a trick where I cannot get the the needle to catch the bobbin thread either when threading the machine or when sewing. I've checked tension, changed the needle, changed the bobbin. I have read the instruction manual and found no clues. Obviously this problem means the machine cannot sew at all. Please help, I need this machine this week. I've a lot to do!