I want to share my experience. This may help you if you are having trouble opening/starting ZD. By the way I have windows XP, but had the same problem with Windows 7.
I had ZD 1.0 installed, a while ago I decided to update it to 2.0.1, followed the instructions and no problem during the installation, BUT when I went to open ZD it would get stuck on the starting window, so the first thing I thought was -have to re-install- so that is what I did... BUT the problem continued... after opening and closing several times ZD opened!!! so from then till now I have been opening ZD by a three step process 1) open ZD, close the window 'cause it would get 'stuck', 2) open ZD, click on the 'stop script' error message and close the window and 3) open ZD and it would go in with no problem. Yesterday it would not open with my three step process, kept on closing and opening and restarting the computer and NOTHING!!!... Solution: turn off FIREWALL for a moment, start ZD and then turn on the FIREWALL again.
For those who do not know how to turn off firewall, go to: START/Control Panel/Windows Firewall
I spent tons of time surfing internet, Zimbra forums for a valid solution, read about the log files, re-installing, lots of other people with the same problem... but could not find the solution, so I just had to click here and there on my computer and find my way around it. I really hope this helps you!! and you have to go through the re-install/logs/hours at the Zimbra forums.