I looked back posts on DMXZone and at the time this problem existed it was related to:
WA - FormToolKit.
See: "Go inside the Configuration/Behaviors/Actions folder and move the Validation Toolkit folder out and up one level. See if that resolves the crash. It did for me."
I'm not sure if this time it is the same issue, some also mentioned Security Assist was the problem but i'm not sure if Form Toolkit is part of SA.