I didn't find a better way to contact the EasyPHP team, so I'm trying the forum.
I just found out that the "document root" string should be trimmed. When you type "C:\projects\project1\ " for example (note the single space at the end), the admin panel do not recognize it as a valid path.
At least on windows, it's impossible to create a folder with a space at the end or the beginning. Just my 2 cents.