This has been bugging me for a while trying out the HelloWorld example with Drools 5.0 M3.
Unable to load dialect org.drools.rule.builder.dialect.java.JavaDialectConfiguration:java:org.drools.rule.builder.dialect.java.JavaDialectConfiguration'
Although it doesn't affect the operation of the DSL file, the error kept popping up on my Eclipse 3.4.1 (Ganymade). Some had suggested to add all the jar libraries to the Java Build Path but that didn't work for me. So, I've removed most of them except the one recommended by the dependencies README.
The following jars are in my buildpath now: