Why is my ebroidery machine suddenly jamming?

Haven't used by Brother 150E machine for a while, but it was perfectly alright when I last used it. Now I find that not only are needles breaking, but the machine is jamming completely. Have taken out the bobbin andsinker plate to clean, but not really fluffy, have now replaced it, changed the needle and still it happens. Feel it is my error rather than the machine at fault, but what am I doing wrong???