Hi Badri,
We regret for the inconvenience caused. I have tested this issue in v.3.2.1.0. I am afraid, I was not able to reproduce this error. I have attached my test sample.
Cusomization Issue.zip
Could you please check the sample and let me know whether you are able to reproduce the issue in this sample?. Does this exception occurs only in your application or in other XPMenus samples also?
Thanks for using Syncfusion products.
Regards,
J.Nagaraj