as of the 0124 and r3338 of the trunk, PApplet#registerSize(Object) is registering objects with the preMethods field instead
of sizeMethods causing:

java.lang.IllegalArgumentException: wrong number of arguments
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at processing.core.PApplet$RegisteredMethods.handle(PApplet.java:693)
at processing.core.PApplet$RegisteredMethods.handle(PApplet.java:686)
at processing.core.PApplet.handleDisplay(PApplet.java:1347)
at processing.core.PGraphics.requestDisplay(PGraphics.java:564)
at processing.core.PApplet.run(PApplet.java:1450)
at java.lang.Thread.run(Thread.java:613)

with libraries trying to register with PApplet. fo the sake of completion, this was happening to me on mac os x 10.4.9
(macbook pro intel core duo) with java 1.5.0_07.

edit]
possible patch

whups, dumb typo. thanks for finding. now fixed for 0125.