Filter Operator Not Supported

When I debug my flash file I get:

“_level0.promotion1.loader_mc.im…”

“im” is an externally loaded MC (published in AS3 flash 9)

When I try and stop at frame 1 with ths code:

ActionScript Code:
[LEFT][COLOR=#000000]([/COLOR]getChildByName[COLOR=#000000]([/COLOR][COLOR=#FF0000]"promotion1"[/COLOR][COLOR=#000000])[/COLOR] as [COLOR=#0000FF]MovieClip[/COLOR][COLOR=#000000])[/COLOR].[COLOR=#000000]([/COLOR]getChildByName[COLOR=#000000]([/COLOR][COLOR=#FF0000]"loader_mc"[/COLOR][COLOR=#000000])[/COLOR] as [COLOR=#0000FF]MovieClip[/COLOR][COLOR=#000000])[/COLOR].[COLOR=#000000]([/COLOR]getChildByName[COLOR=#000000]([/COLOR][COLOR=#FF0000]"im"[/COLOR][COLOR=#000000])[/COLOR] as [COLOR=#0000FF]MovieClip[/COLOR][COLOR=#000000])[/COLOR].[COLOR=#0000FF]gotoAndStop[/COLOR][COLOR=#000000]([/COLOR][COLOR=#000080]1[/COLOR][COLOR=#000000])[/COLOR];

[/LEFT]

I get the following error:

ActionScript Code:
[LEFT]TypeError: [COLOR=#0000FF]Error[/COLOR] [COLOR=#808080]*#1123: Filter operator not supported on type mcPromotion.*[/COLOR]
at BannerClass/navigate[COLOR=#000000]([/COLOR][COLOR=#000000])[/COLOR]

[/LEFT]

Adobe does not seem to document this, except for a short description on the Error Messages page

Does anyone know what might have gone wrong?