Hi Hanan,
I've seen this problem too... It occured for me when using the CVI 6 beta version. (I also had version 5.5 installed)
Everything worked fine for a while, and then each time I tried to use the interactive windon, it froze the system...
I was told that this was a known bug with the beta 2 release, and would be fixed in the final release.
Sure enough it was...
However, if you have multiple versions of CVI installed on your machine, it may be worth checking that they are using the correct version of iw.exe for that version... Try locating all the copies of iw.exe on your system and checking which is the right version (right click on the exe file and go to properties, version) try renaming any other versions and see if your problem still exists...
Don't kno
w if this will fix your problem, but I remember playing around with this when I had the problem...
Hope this helps