Just got RimWorld. Every time someone visits, it doesn't matter if they're friendly or not, they twitch once then stand around at the edge of the map. After a while they starve or start attacking each other.

I can go trade with visitors (sometimes there is a question mark floating above one of them) but there isn't much point as they soon die anyway.

Is this a known bug? I can't find any reference to it online.

[edit] Pretty sure it's a bug, from output.log: ("Blur" is the name of a raider)

Blur threw exception while determining job (constant): System.NullReferenceException: Object reference not set to an instance of an object
  at RimWorld.ThinkNode_DutyConstant.TryIssueJobPackage (Verse.Pawn pawn) [0x00000] in <filename unknown>:0 
  at Verse.AI.ThinkNode_Priority.TryIssueJobPackage (Verse.Pawn pawn) [0x00000] in <filename unknown>:0 
  at RimWorld.ThinkNode_Conditional.TryIssueJobPackage (Verse.Pawn pawn) [0x00000] in <filename unknown>:0 
  at Verse.AI.ThinkNode_Priority.TryIssueJobPackage (Verse.Pawn pawn) [0x00000] in <filename unknown>:0 
  at Verse.AI.ThinkNode_Subtree.TryIssueJobPackage (Verse.Pawn pawn) [0x00000] in <filename unknown>:0 
  at Verse.AI.ThinkNode_Priority.TryIssueJobPackage (Verse.Pawn pawn) [0x00000] in <filename unknown>:0 
  at RimWorld.ThinkNode_Conditional.TryIssueJobPackage (Verse.Pawn pawn) [0x00000] in <filename unknown>:0 
  at Verse.AI.ThinkNode_Priority.TryIssueJobPackage (Verse.Pawn pawn) [0x00000] in <filename unknown>:0 
  at Verse.AI.Pawn_JobTracker.DetermineNextConstantThinkTreeJob () [0x00000] in <filename unknown>:0  lastJobGiver=

Bug report on forum: https://ludeon.com/forums/index.php?topic=21587.0

(includes potential solution: uninstalled on D: reinstalled on C: and used Phoebe AI)