Neutral Hostile attack delay?

I was setting up some neutral hostile units to act as active obstacles in a map. When a player unit comes near to them, they're supposed to attack it. However they don't seem to be very happy about that.

When I approach them with my units, they take a couple of seconds to register that my unit is in range before they attack it. Sometimes it's quicker, sometimes it's instant, sometimes it takes up to 3 seconds for it to actually fire.

They aren't sleeping (time of day is high noon and they're set not to sleep anyways), their range values are correct, but I can't figure out why they take so long to take a pot shot. Anyone have this problem before?

EDIT: Arg, dumped this in the wrong forum, someone care to move this to general dev? Sorry!

no, man. the question is ok here for me

you know.. i had this problem before and finally i had to use a player slot.
neutral passive and neutral hostile plays as computers yes or yes.

all player slots are there waiting to be used... so. try to avoid using neutral passive or hostile. ( only use neutral hostile for creeps ).

all right. c ya.

i mean.. the AI control$ both neutral pa$sive and hostile.
so.. u can order a unit to do something by triggers but... at the end it will do what the AI wants.

adios.!