Version: BluePower 1.7.10-0.1.700
Location: Qmunity Sub Server
Breaking or placing a Retriever at the end of a set of Pneumatric Tubes with items in output slot hydraulicraft Crusher machine will crash client.

Can be reproduced every time. If items are not in the output slots when breaking or placing Retriever client will not crash.
http://pastebin.com/ZMVMnU6x

Just tested with;
Vanilla Furnace: no crash
IC2 Electric Furnace: No crash
Factorization Slag Furnace: No crash
hydraulicraft High Pressure Pump with Charcoal input slot (like you would normally do that, but for quick testing purpose): Client Crashed