I created my music collection by finding music in the My Music folder.
Sometimes I download some more albums and store them in that folder.
When I try to update my collection by finding music in the My Music folder again the program shows the progress bar till it comes to 100 % and than hangs on the last directory and doesn't respond anymore.

After scanning all your music folders for files the program has to compare the files it found against the ones in its database in order to remove existing ones from the list and show only new files. It may take some time. If you scan your entire folder every time, there may be quite a lot of records, which is why you may think that the program hangs.