posible bug

Was doing some skills work, using two necklaces that are dibilitating enough to make me kill less quick and so prolong fights. This log shows me removing the necklaces when I am alive happy and well and then when I go to use them, they kill me. It seems very odd that this should happen and I wondered if it was a bug, purely because if my hps are X with them both on and I remove them my hps should still be X, so if I wear them again I should not die as it has never happened before. <13%hp 100%m 100%mv 6059tnl> rem necklace rem necklace get caYou stop using necklace of Vis'pa. <11%hp -5%m 66%mv 6059tnl> You stop using necklace of Vis'pa. <10%hp -2%m 50%mv 6059tnl> get cake knapsack;eat cake get cake knapsack;eat cake You get chocolate cake from a cowhide knapsack. <10%hp -2%m 50%mv 6059tnl> You eat chocolate cake. <10%hp -2%m 50%mv 6059tnl> You get chocolate cake from a cowhide knapsack. <10%hp -2%m 50%mv 6059tnl> You eat chocolate cake. <10%hp -2%m 50%mv 6059tnl> get cake knapsack;eat cake You get chocolate cake from a cowhide knapsack. <10%hp -2%m 50%mv 6059tnl> You eat chocolate cake. You are sober. You are full. <10%hp -2%m 50%mv 6059tnl> drink mug drink mug You drink firebreather from a pewter mug of Gods' Wrath. You feel tipsy. You are full. <10%hp -2%m 50%mv 6059tnl> wIt is already empty. <10%hp -2%m 50%mv 6059tnl> wear necklace wear necklace wYou wear necklace of Vis'pa around your neck. You feel a deathly chill as you wear necklace of Vis'pa. You lose the insight into pathfinding. Your feet feel a light cooling as you tug off some leather traveling boots. You have died, but the Carrion Fields are not finished with you yet! Your soul is returned to the realms in the form of a ghost. You will return to your corporeal state in a short while. Be careful, for even a ghost should fear some dangers! <0%hp 0%m 50%mv 6059tnl> whe You do not have that item.