After our upgrade to CRM 2013, we are getting this error when the form opens but only occasionally. We are using Silverlight webresources and use the JavaScript Onload event to access the WebResource and call a method in it. This works ok most of time but the following can happen:
1. Open a Create new form that has an onload event calling the webresource
2. Message box pops up with the error "There was an error with this field's customized event" Field: Window Event:onload Error: blank.
3. Close the form window
4. Open the form again, no issue reported and the onload function works.
5. Open the form again with data or another new entity and the onload function works.
It seems as if that form has been open / loaded before it works but first time it fails with this error. This happens on any entity form that we have customized, first time the onload fails, subsequent times it works ok.
Has anyone come across this before? Many thanks, Caz