Please follow the steps below...
1) Clear all the browsing history & Cookies from the browser you have used for OPAC.
2) Stop the server
2) Delete newgenlibctxt folder from the path C:/NGL3/apache-tomcat-6.0.32/webapps/newgenlibctxt
3) Delete newgenlibctxt folder from the path C:/NGL3/apache-tomcat-6.0.32/work/Catalina/localhost/newgenlibctxt
4) Run the server and check the OPAC
After this process also if you have the same error.
Send the server error screenshot and the details of the NGL Version you are using.
NewGenLib Open Source Support
Verus Solutions Private Limited