This error message is quite odd and we have not received such reports so far. Could you confirm whether you are using the most recent build version of WebScheduler 3 (WebScheduler 3 build 130 and WebUI.NET Framework 3 build 801) on your Web Site/Web Application project?

I tried to reproduce the problem in my local test by modifying Exporting_Timeline.aspx sample file of WebScheduler Samples project; view the modified page in browser; and export the Timeline view into pdf format but my efforts were not successful – everything worked smoothly and the exported document was accessed without any issues.

I’m willing to advise you further but in order to do so I would need you to elaborate on your specific scenario and possibly give me a running simple sample that replicates the issue – you may modify Exporting_Timeline.aspx sample file so that the reported problem is reproducible then have the sample sent to us to be investigated further – and a step by step guide that we can use to observe the problematic behavior.