Could not upgrade RDL on Report

You may get an error that contains the following message:

And the additional information looks similar to this:

This happens if you are working on an older version of NAV that works with C/SIDE and text file import. The compiler needs components from the RDLC Report Builder installation when importing a text object. If you have had multiple versions of NAV on your system, then one version may have overwritten the correct version of the components with newer versions. 

You can reinstall your report builder from the NAV DVD installation image. The MSI you need to run is most likely installed at this path:

After running the setup, the Designer should be able to save the report.