Assertion failed: IsValid() File:D:\BuildFarm

We were able to reproduce this crash in a clean project. We have written up a report (UE-23217) and it has been submitted to the developers for further consideration. I will provide updates with any pertinent information as it becomes available. During testing we found that the issue was caused by closing the animation and timeline windows. Thank you for your time and information.


Window > Reset Layout will allow you to open the blueprint again.


Make it a great day

Wow IT REALLY WORKS! Thank you!

nice trick! thank you

also helped me. Thanks!

Thanks, it works with the release version of 4.10 as well.

I had this same issue, and posted a Bug Report on AnswerHub here:

I posted the answer provided here on my post.

I want to confirm that this workaround works on both the Windows and the OS X binary versions of 4.10.0.

It’s worth noting that while this workaround does work, keep in mind that once in UMG you can not change your layout i.e. close the animation boxes, or the crash will occur again. Hope a hotfix comes soon. Thanks for the workaround anyway, I was worried it may have been a source control issue (my project is github.)

WOW it works ! thank you, i thought i was doomed !

YES! That what I want!!! it’s back to work fine! :smiley: