[Pharo-dev] Problem to save packages

Hi, I'm a new Pharo user (Pharo 5.0). I have created a package and now I just want to save it in the package-cache folder. But, when I try to do this using the Monticello Browser, I get an exception telling me the file I'm trying to save does not exist. I already managed to save some packages but I can't anymore. Thanks in advance for your help.