We have tried to reproduce the exception, but with no luck. I have attached my test project, it could be great if you could check it out and let us know if we differ in something. Please note that when save/load layout is used instead of an elements with no SerializationTag new elements are generate and this in some scenarios might lead to null reference exception. So setting SerializationTag could fix the issue.
If that doesn't help it would be great if you could send us a simple project where the exception is reproduced or a simple code.
the Telerik team