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(at)163(dot)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?