MyEclipse with Tomcat: Bad version number in .class file

The above error occurs when the MyEclipse Compiler uses different version of JRE in relation with the Tomcat JRE version.

Please, for the MyEclipse check:
Windows > Preferences > Java
1. Compiler
2. Installed JREs

For the Apache Tomcat check in MyEclipse Server View:
Apache TOmcat > Configuration > Tomcat > Tomcat 5.x > JDK