Re: java.lang.VerifyError running Eclipse project

I am getting the following error when I run my Eclipse RCP application:

java.lang.VerifyError: (class: com/mybiz/myproj/model/ResultsModel, method:
buildModel signature:
(Ljava/lang/String;Lcom/mybiz/myproj/search/DocumentType;Z)Ljava/util/List;)
Incompatible argument to function

which I don't comprehend. The actual signature for the buildModel() method
is:

List<String> buildModel(String, DocumentType, boolean)

so it seems to have lost the boolean 3rd parameter unless that's what the Z
indicates in the error? I only added this boolean parameter recently.

What could be causing this error? Figuring it's a stale class definition
floating around somewhere I have done a clean and build but it hasn't
helped.

Curiously, this method references a class from another Eclipse plug-in of
mine and if I comment out references to that class then I don't get the
error (although the code doesn't work of course!). So why would referencing
a foreign class somewhere in the method definition cause Java to think that
the signature of the method is wrong?

Any ideas?