Hi !
I downloaded Trung's application and can confirm the same error.
I then built a new FCKLibrary DLL, after updating from Gizmox SVN. Then downloaded FCKEditor's newest version and thereafter their nightly build version Error shows in all above cases.
Created a new project from scratch, in case there was something within Trung's project, but error still shows.
Error is however only in IE (IE7 in my case). No error in FF3.
Tested in VWG 6.2.2a NET3.5 VS2008 SP1.
Palli