Some Quests won't finish or quest items won't drop

This sounds very unusual, would you mind mailing me a screenshot to rory@grindinggear.com of you having killed the weaver and the spear not dropping, with your quest log open on that quest? It might be something about the location and position of the boss that is preventing the spear from spawning.

As for the Lurker, that sounds like it shouldn't be possible. What skills were you using to kill the boss? Were degeneration effects like Viper Strike, Burning+Elemental Proliferation, or minions involved?