There are a number of threads of things to watch out for if one treats a lot of files in one go:
Are the files OK?
See here for tools to check them:
Also, it may be worthwhile to treat only those files that really need treatment. So use a filter like %title% MATCHES "(?-i)The "
Which other programs may block the access?
Are the access rights OK for all files?
Does the freeze happen always with the same file(s)?