When I copy a shape in my application and then attempt to paste it, I get the error shown in the attachment.

Transcribed:
The Paste transaction FailedRolledback
Error Log:
1. Paste failed on a single node: Object reference not set to an instance of an object.

Can someone give me hint for where to start looking for what I've done wrong?

Thanks,
Herb.

The information you've provided is not enough to conclude what the problem is. I advise you to send the sample project in which this error occurs to support@nevron.com and we'll tell you what's wrong with it.

I don't know how little code I can use to reproduce this.

It's occurring in a very large project that I can't send, for obvious reasons.

I've created my own library of shapes with custom objects attached to the tag property of the shape. Is it possible that this is causing problems with copy & paste?

Herb.

Most likely this is the problem. In order to solve it, make sure that your custom objects are deep cloneable (i.e. implement the ICloneable interface for them).

I had the same problem and I had added ExpandableObjectConverter to my class. As soon as I removed it, all is well