I have experienced a similar problem in A2k and A2k4
If I start the Vlide editor and toggle back and forth between the windows by clicking on the taskbar icons after a couple of times, the vlide editor will not allow me to edit the code as if there is a function running in the background, but there is no function running and unless I close the vlide editor and reopen it, I won't be able to edit the code in the vlide window. BUT, if I open the vlide editor and then toggle back and forth using -vlide in the command line and the "return to AutoCAD" button the behavior does not exhibit itself.