I would suggest updating your servers to SP1 in the very least. We have several Windows 2003 serves with SP1 and have encountered minimal issues with the SP. Also, check compatibiliy listings w/SP1 just in case. ETrust (CA) is supported. The article you provided is for NT4 (Irpstacksize). This is not an issue here but some TCP and IPv6 issues have been addressed in SP1.