Aha! I found the problem. Later on in the script, some changes were made to the newly copied files--that is, a reader handle was opened on it, the unaffected parts were copied to a writer handle (opened on filename.ext.new), the new data was sent to the writer, and the remainder of the file copied over as well. Then the streams were closed, the original was unlinked, and the .new file was renamed in it's place. The umask was causing problems with the new file that was created by the writer, and setting umask(0) fixed it. Silly me. =) Thanks for the help guys!