R cannot be initialized. Exception occured during R initialization.

Dear Community, 

I recently upgraded from KNIME 2.11 to KNIME 3.3 on Windows 7 using the self-extracting zip installation. 

I have been using the R statistics integration nodes in 2.11 but now I cannot initialize those nodes. 

At the beginning, KNIME console threw the message related to R library "Rserve" was not installed. 

But after the installation, I still cannot initialize the nodes. 

I wonder if anything else I can check. 

Thank you, 

Rae