BUG #4694: uppercase path cause postgres can't start

The following bug has been logged online:

Bug reference:      4694
Logged by:          trainee
Email address:      trainee12@163.com
PostgreSQL version: 8.3.6
Operating system:   windows xp
Description:        uppercase path cause postgres can't start
Details:

I download zip binaray 8.3.6
extract into e:\postgres

set system variables "path"  add "E:\POSTGRES\PGSQL\BIN;" --uppercase

cmd;

pg_ctl register -N postgres -D "e:\postgres\pgdata"

when I start server , failure

error msg is :

LOG:  could not open directory "/share/timezone": No such file or directory
FATAL:  could not select a suitable default timezone
DETAIL:  It appears that your GMT time zone uses leap seconds. PostgreSQL
does not support leap seconds.

if I change  system variables "path" into lowercase, success.

why?