san_meide,
Apart from Sonar for eclipse plugin, did you install Sonar server in your local system ? You can test the Sonar server connection in MyEclipse from Windows > Preferences > Sonar > Servers > Edit > Test this connection.
For information on installing Sonar server, please take a look at the following links –
http://docs.codehaus.org/display/SONAR/Using+Sonar+in+Eclipse
http://choudhury.com/blog/2011/06/11/setting-up-sonar/
http://stackoverflow.com/questions/16191413/associating-a-project-to-sonar-in-eclipse
Can you please check whether the Sonar for eclipse plugin is working fine in the base eclipse. For example, if you are using MyEclipse 2013 then the base eclipse is Eclipse 3.8, if you are using MyEclipse 10.7 then the base eclipse is Eclipse 3.7, if you are using MyEclipse 9.1 then the base eclipse is Eclipse 3.6.
If you are still facing issues in MyEclipse, can you please answer some more questions to help us investigate further:
1) Can you please share your installation details from MyEclipse > Installation summary > Installation details ?
2) Can you please mention the exact steps in detail to help us replicate the issue at our end ?