I created a new project and copied the assets folder out of another. I tried adding an icons from the Social Icons set to a button from the Adroid set and then got an error. I exited the program and went to open the screen and it now says

Could not open the editor: org.eclipse.core.internal.resources.ResourceException: Resource '/Round%20Trip' does not exist.

Looks like the error goes away if I remove spaces from the parent project folder name and screen name itself... Weird

Richard, can you send me your log file as generated by Window > Preferences > WireframeSketcher > Report a Bug? I am looking to reproduce the "spaces" bug for some time now and your log will help me to reconstruct your setup.

Just emailed it then :)

Got it. Thanks!

Thank you for the log file. It helped me to locate the issue. It only occurs when custom icons are used in projects with spaces in their names. It will be fixed in the next release.