I'm also having a similar issue with 2.71. I made up some presets in a user patch. I then decided to start over and erased all of the blocks with the "action" button and the "delete all blocks" switch. I loaded in some new blocks and there is no sound coming from them. Everything works fine on new patches but I can't reuse the deleted ones.
I might have to go to 2.70 but I'm concerned that it might mess something else up.