OKay, now i see what the problem: <weak registry protected> <finalize items> <HostSystemMenusProxy>>finalize> .... <HostSystemMenusProxy class>>unregister> <weak registry protected> In my WeakRegistry, a #finalize message sent while registry semaphore locked, so, in case if object in #finalize trying to manipulate with registry then it going to deadlock. Then following piece: WeakRegistry>>finalizeValues self protected: [ valueDictionary expiredValuesDo: [:finItem | finItem finalizeValues ]. ]. should be rewritten as: | expired | expired := OrderedCollection new. self protected: [ valueDictionary expiredValuesDo: [:finItem | expired add: finItem ] ]. expired do: #finalizeValues. But either way, HostSystemMenusProxy should not attempt remove itself from registry during #finalize (and causing a deadlock), since its pointless. -- Best regards, Igor Stasenko AKA sig.