I'm afraid this is Dy Design.
By request, 2.43u allows the cost multiplier to go negative. This is by design. I will probably add a checkbox to allow the user to prevent this and prevent it from going below 0 like before if they like, but going negative is what it is suppose to do currently.
You sim's not frozen, it's just running really really slow and because VB6 is single threaded, the UI won't respond for tens of seconds or more. The popualation looks like it's only 500, but there are actually several thousands corpses all in a tight pile with the bots. Tight clusters of bots are really slow because of the way vision works. Calculating who can see what, etc.
I'm running your sim now and it is slowly correcting. CostX is climbing, corpses are expiring, the blob is expanding and the sim is running faster....
I'll add the checkbox in 2.43v.