Servlet class cannot be loaded

Hi,

I am trying to migrate my servlet from Netweaver 7.0 to 7.3. However, when I try to run it in NW7.3, it gives the error :

Error: Servlet with class <i>[xxx]</i> cannot be loaded.

Troubleshooting Guide https://sdn.sap.com/irj/sdn/wiki?path=/display/jstsg/home

Details:     You can not invoke the Servlet only by using its name

I have run out of idea what could be the problem. Please help.

Thanks.