I have duplicated the hang on "sce-import -d" which is probably where sce-update hung if I manually add an entry to a .dep file that creates a circular dependency. I tried to create a circular dependency with sce-import but it would not let me even if the offending entry in a dep file was 2 or 3 dep files deep. So as long as sce-import is used to create the dep files, it should not result in problems. Please understand that manually created dep files can result in errors.