I received the following bug report to the Vulture's Claw project but it looks like a Slash'EM problem:
From Paniclog file:
0.0.7E7F3 20090528: impossible select_off: a heavy iron ball (chained to you)???
Once I had ball chained to character i pick it up and it shown in inventory then I tried to drop it and was unable, anyway - strange behaviour.