MDS window disappears for JDE 4.0

[Mita]

I have installed both JDE v3.7 and JDE v4.0. For the v3.7, the MDS
simulator runs fine and I can use the web browser for viewing pages.
But the v3.7 does not support javascript and I need to have javascript
support for viewing my application. That is why I downloaded the JDE
v4.0 since it supports javascript. But for the JDE v4.0, the MDS
simulator does not run. The window opens and closes immediately.
Anybody, any ideas? Any help will be appreciated.

Thanks