Some JBT plugins have the J2SE-1.5 execution environment set although they use classes/methods that only exist in JDK 6.
The following plugins:
contain compile errors if there is JDK/JRE 1.5 in the workspace. Since the classes/methods that are being used aren't a part of the language, but a part of JRE, Eclipse can't find those errors because there is only JDK/JRE 1.6 in the workspace.
The solution is to change the execution environment to JavaSE-1.6