Constant errors

I keep getting these errors in the error log -:

Error in JDT during AST creation. Problems when calling code from a plugin: "org.eclipse.jdt.ui".

From time to time, a pop-up message appears indicating that:

An internal error occurred during: "Evaluate launch button prompt". org.codehaus.groovy.runtime.DefaultGroovyMethods.plus (Ljava / Util / List; Ljava / Util / Collection;) Ljava / Util / List;