Level Design Random Crash to Desktop

[Killer9999]

Build KillingFloor_Build_[2009-02-09_10.82]

OS: Windows NT 6.0 (Build: 6001)
CPU: GenuineIntel PentiumPro-class processor @ 2393 MHz with 2047MB RAM
Video: NVIDIA GeForce 8600 GT (6906)

Assertion failed: inst->KPhysRootIndex != INDEX_NONE && inst->KPhysLastIndex != INDEX_NONE [File:.\KSkeletal.cpp] [Line: 595]

History: KInitSkeletonKarma <- KInitActorKarma <- AActor::setPhysics <- UObject::ProcessEvent <- 
(WaterVolume KF-Castle_A7.WaterVolume3, Function Engine.PhysicsVolume.Touch) <- TouchTo <-
 AActor::BeginTouch <- ULevel::CheckEncroachment <- ULevel::SpawnActor <- (ZombieClot) <-
 UObject::ProcessEvent <- (KFGameType KF-Castle_A7.KFGameType, Function KFmod.KFGameType.MatchInProgress.Timer) <- 
AActor::Tick <- TickAllActors <- ULevel::Tick <- (NetMode=2) <-
 TickLevel <- UGameEngine::Tick <- Level Castle <- UpdateWorld <- MainLoop <- FMallocWindows::Free <- 
FMallocWindows::Realloc <- 4C576C61 0 FArray <- FArray::Realloc <- 0*2 <- FMallocWindows::Free

No idea why this is doing this. I do not touch Karma stuff or coding stuff or any of that... Also does not appear to be happening at the same time and not all the time. Recorded happening on solo and whilst hosting a game. Also it should be noted this does not occur on the computer the map was created on. Any Help would be great as I've double checked all changes since the previous version and I have had no luck at all

Edit: on review this looks like a clot fell into a water volume and caused this problem but is this a KF problem or have I done something wrong in my water volume?