Unnamed selector error message

[Roberto]

hello, I try to develope a portal with cocoon, but I obtain this error message when I try to do some modifications on my sitemap.   UnnamedSelector: ComponentSelector could not find the component for hint []   But the strange is that when I restore my old sitemap ( that worked well ) I obtain the same error message! I try to reboot my system, but it doesn't change anything. The only way to resolve the problem is to re-install cocoon,  put my old sitemap and all work well... How can I resolve this problem? If anyone speak italian I think that I can explain better the problem. Thanks. Roberto