I keep getting this error

[Guest]

I keep getting this error ..however sometimes the error did not happen what is this error means?

TypeError: Error #1009: Cannot access a property or method of a null object reference.

          at AS3_fla::MainTimeline/frame325()[AS3_fla.MainTimeline::frame325:2]

          at flash.display::MovieClip/gotoAndStop()

          at AS3_fla::MainTimeline/fl_ClickToGoToAndStopAtFrame_17()[AS3_fla.MainTimeline::frame446:12]

[Ned Murphy]

The 1009 error indicates that one of the objects being targeted by your code is out of scope.  This could mean that the object....

- is declared but not instantiated

- doesn't have an instance name (or the instance name is mispelled)

- does not exist in the frame where that code is trying to talk to it

- is animated into place but is not assigned instance names in every keyframe for it

- is one of two or more consecutive keyframes of the same objects with no name assigned in the preceding frame(s).

In this case, the error is indicating that whatever object is being targeted in lIne 2 of frame 325 does not exist as far as the compiler sees it.