Hello Peude,
Are you using the Binary (Launcher) or Source (Github) version of the Editor? Also, are you importing the new object mesh from a disc, a USB or from your hard ?
If there are any output that are provided from this error, or even a crash reporter due to the Engine not responding, please provide those to us. You can locate output from the Engine by going to: PROJECTNAME/Saved/
Looking forward to hearing from you!