When working with files of the form:

@@@@@@@80@@XXX_XXX@FILENAME.LIS

filesize() and filemtime() return an error of:

Warning: filesize() Stat failed for FILENAME (errno=2 - No such file or directory) in /path/to/program.name.php on line 100

The same error occurs with PHP 4.2.X. Using PHP 4.3.1 with Apache 2.X on a windows system does not reproduce the error.

If the filename is changed to:

@P@@@@@@80@@XXX_XXX@FILENAME.LIS

the error does not occur.  The list of files in the directory was obtained using the PHP readdir() function, so i know PHP is finding the file at sometime, just not for filemtime() or filesize().