Yep they're very temperamental, but damn such a powerful block. Most of the times I think the bug can be avoided by hooking up power to them last after they're completely configured. Also by not breaking a chest while it's still attached to a working manager. Third don't put in any of the new tree saplings from forestry like cherry sapling. Apparently redpower doesn't know they exist, and it does the null item thing.
YMMV.