javascript error message when applying behaviors

hello ! who can help me ?

I just upgraded from DW4 to DWMX2004. Now on my navigation bar ( on which I have several behaviors applied, namely swapImageRestore and ShowHideLayers ) I had to change a layer and as I want to re-apply the behavior, I get an error message saying:" When executing Onload in Swap Image.htm, the Javascript error(s) occured: getDocumentDom: The argument number 1 is not valid".

then, when I click OK, it tells me a second error message that a particular Swap Image.js:" document.MM_NS_REFS has no properties.

Then in the behavior's open box, it tells me that no images where found...???

Please it's urgent I solve this problem, should I perhaps reinstall the program ??

thanks for helping

Johnnymichael