There seems to be a problem with the sort command when using the -k option. If you look at the Example 1 below you will see that I am trying to order the output by file size, yet if you look closely:
the files backuptest270803.gz, uk-re_bac.gz appear below tms_mp2.zip. It seems there may exists a problem with large file sizes as in Example 2 the problem does not occur.