Ragdolls turned into Props

Howdy Folks,

… so, apperantly some of my ragdolls turned into some kind of weird stiff prop.
They spawn in a T-Pose and with a Physics model, big as a truck below 'em.


I haven’t checked all of the ragdolls but so far, this anomaly only appeared on L4D1 characters (Standard and costumized models).
Any idea what could cause this or even better how to fix it.
Have not changed or played one bit of g-mod for 3 month.
Quite the contrary, I even deleted and re-installed it after I encountered this issue. (Lost all of my savegames in the process-.-)

I’d be very grateful, if you can help me.
BTW, if it’s any help:
Before i started G-Mod again, i switched my graphiccard from a GT430 (Nvidia) to a HD4850 (ATI).
I doubt that it caused it but what do I know …

Thank you for any help.