Error executing code: Wrong argument type for function (while saving Sales Order document)

Hi,

I have introduced Sales Order creation date & time (createdDateTime field of SaleTable) in the Sales Order document which is working fine with many users. But some users facing problem while saving the document (as PDF) with following  error:

Error executing code: Wrong argument type for function.

(C)\Classes\PDFViewer\writeDateTime - line 4

(C)\Classes\ReportOutputUser\writeField

(C)\Classes\ReportOutputUser\printViaClass

(C)\Classes\ReportViewer\printPDF

(C)\Classes\ReportViewer\printToTarget

(C)\Classes\ReportViewer\dialogAndPrint

Kindly advise about the possible reason and solution.

Regards...