Once in a while, though, the export process would throw the dreaded and unhelpful Sys.WebForms.PageRequestManagerParserErrorException exception.
Eilon Lipton's helpful post gave a handy checklist of things not to do, but in spite of ensuring all the common causes were accounted for, it would still occur occasionally.
function onExportClick(sender, args)
The error itself points you in the right direction, but some more context sure would be nice. Anyway, apparently this script mitigates situations where the Telerik controls are still in the process of being rendered when the full postback is initiated, corrupting the Response header in the process.