The signature of this method differs between NLOG4j and log4j.

log4j: Category.log(Priority, Object)
NLOG4j: Category.log(Priority, String)

Code compiled against log4j throws this exception when using NLOG4j:
java.lang.NoSuchMethodError: org.apache.log4j.Logger.log(Lorg/apache/log4j/Priority;Ljava/lang/Object;)V

Changing the method signature to (Priority, Object) fixes the problem.

Problem observed in NLOG4j 1.2.25