Error inserting JSON string to Postgres DB

Hi,
I am getting Cannot have quote-char in plain field:['{"] error when trying to insert a JSON string into a Postgres DB table using JDBC request.
I tried the following but nothing worked:   
   - place the JSON string in single quotes, 
   - escaping the double quotes with \", 
   - placing the string in $$<JSON string here>$$ but nothing worked. 
There is no issue with the connection and other select/insert queries and I was able to insert from pgAdmin with the same string in single quotes though.
The JSON string looks like this: {"A":"A", "B":[{"C":"C"}]}
I am really out of ideas at this time. Can someone help?
Thanks,Jun