Filemanager -showModalDialog problem

Hi all!
I have this problem on a win2000 machine(sp4). IE6(sp1).

When I click the toolbar.button to insert an image the dialog with the image-properties is opened..so far all is fine..
however..when I click the Browse on server (which should open up the FIlemanager) all i get i a quick blink(as if the form is posted/script is run) and then nothing happens..no Filemanager turns up...

What makes this very interesting(and annoying i might add) is the fact that on another computer with the same win2000-setup all works just fine...Ive tested on a lot of other setups and it works just fine...

I have so far tried:
- Updating with all patches from MS..
- Lowered all settings on security
- Enabled all i can think of in Options/Advanced...
- Tried opening a window with a standard window.open..dont work..
- checked for spyware/virus
- searched on the net for anything i could think of that could be related...

also made some testing and found that the actual problem seems to be that the window opened with window.showModalDialog (which is what fck uses to open the imagedialog) cannot open a new window...if i open a new window with window.open and then let this open a new window it works..



please, if anyone knows what is going on..help!