One day I found that I couldn't open my existing projects under Cubase LE, it was hanging while loading MSI. The standalone worked, though.
I googled the problem, and read that some people had found this happened after they had installed IE8.
Hard to believe, isn't it ?
Well... then I realized *I* had installed IE8 recently

Thus I uninstalled my IE8, this brought me back to IE6 since I had never got IE7.
After that, believe me or not, everything was OK again !!
Then I installed IE7, and everything still works fine !
I've read about people having the same problem with another host, therefore Cubase LE isn't responsible for that.