Exception when opening a WYSIWYG dialog in FF2.0

[Exception... "Component returned failure code: 0x80070057 (NS_ERROR_ILLEGAL_VALUE) [nsIDOMRange.setStartAfter]" nsresult: "0x80070057 (NS_ERROR_ILLEGAL_VALUE)" location: "JS frame :: http://localhost:8080/xwiki/com.xpn.xwiki.wysiwyg.Wysiwyg/824261187A53774A50546E8219690100.cache.html :: com_xpn_xwiki_wysiwyg_client_dom_internal_DefaultRange_$setStartAfter__Lcom_xpn_xwiki_wysiwyg_client_dom_internal_DefaultRange_2Lcom_google_gwt_dom_client_Node_2 :: line 13943" data: no]
[Break on this error] this$static.getJSRange__().setStartAfter(refNode);

function com_xpn_xwiki_wysiwyg_client_dom_internal_DefaultRange_$setStartAfter__Lcom_xpn_xwiki_wysiwyg_client_dom_internal_DefaultRange_2Lcom_google_gwt_dom_client_Node_2(this$static, refNode){
13943 this$static.getJSRange__().setStartAfter(refNode);
13944}