When using SIGMA under Tomcat, and creating a IM connector, you may encounter a situation where you get an error concerning not being able to load TEWS client.
This may be caused by the absence of the endorsed folder from the root of Tomcat folder.
Under the SIGMA installation folder you will find the java endorsed files (for example C:\SIGMA\SIGMA\jdk-endorsed-jars).
Copy them to the JRE location and the root of Tomcat. For exmple:
C:\Program Files\Java\jdk1.6.0_45\jre\lib\endorsed
and
C:\Tomcat 7.0\endorsed
Restart Tomcat and try to start the connector.