After upgrading to C3/RO87789 or C4/RO89796 you will experience the above error when attempting to view log files for the Data Importer, or the exported report results in an email notification.
This is caused by an entry stated within the patch ReadMe to add the following line in the web.config file in the Web Server folder:
Add below line under ‘httpModules’ section.
<add name="QueryStringModule" type="CA.Common.Web.HttpModules.QueryStringModule"/>
****** Do not add this line or remove and then run an iisreset and verify the error is not generated.
This information as now been removed from the patch ReadMe file.