Sequencer can't trigger samples

[B.B.]

Is there anybody that has an idea why the sequencer suddenly can't trigger samples anymore I've made with my mc 808?
What I can trigger are my old samples that are saved into the memory for a while now. The new samples can only be triggered in individual user patterns and when I switch manualy from the current user pattern to the next following pattern(U001-U002 or U008 - U009). When I play a pattern that doesn't contain a sample and I switch to another pattern that does contain a sample, the sample won't be triggered. Also samples are not being triggered the song mode... what to do,?