Web Custom Screen - Errors

Hi, I have a web custom screen (ASP.NET based) which runs perfectly ok in a browser. When I added it to Tessitura as a custom screen it renders ok and can pull the details for the current constituent from the local tables without any problem but:

1.      On some workstations, anytime we click on a button or list item which does a postback, we get the error shown at the bottom. Setting EnableEventValidation="false" at the page level or in the web config file stops this error on the problem machines but make some controls irresponsive.

2.      Clicking on a listbox or a drop down list item doesn’t fire the associated event, we need to select an item by using the up/down arrows and then press enter to make it work. We have seen similar issues in case of some dashboard widgets.

Postback Error when called inside Tessitura as a custom screen or a report:

Sys.WebForms.PageRequestManagerServerErrorException: Invalid postback or call back argument. Event validation is enabled using <pages enableEventValidation=”true”/> in configuration or <%@ PageEnableEventValidation=”true” %> in a page. For security purposes, this feature verifies that arguments to postback or callback events originate from the server control that originally rendered them. If the data is valid and expected use the ClientScriptManager.RegisterForEventValidation method in order to……… Do you want to continue running scripts on the page?

I am using the execute local procedure web API to update the local tables.

Any ideas? Thanks!

Mo

National Ballet of Canada