Unknown crash, also crashes debugger (screenshot, code)

ms = []
for i,m in enumerate(skeleton): 
   ms.append({'x':0, 'y':0, 'mid':m.Value('mid')})
theserver.SendToAll({'action':'updatemonsters', 'monsters':ms})[/code:1tzmwvuw]

Here's what the debugger spits out when this code is run:

<img src="http://i.imgur.com/wjC6w.png">

mid is a valid private variable of the skeleton type. The server code never gets executed, but in any case it works (if you simply remove the 'mid' entry from the dictionary, this code executes fine).

I'm really going mad, because the networking code was enough of a hack as-is. Then I had the horror of using SOL.<sprite> to get object handles. And now this. GAH.

EDIT - Incidentally, there is no Event 0 in Layout 1, and this is happening in Layout 3 which makes me think the error message is just a default and I've managed to make something really bad happen.