euro bb help

[motomagII]

right daughters friend has got jump bike with euro bb set unsealed bearings .i set  it up and tightened it last night and basically it still keeps coming loose.
i removed the screw in part and greased then put this back in till the bearings ran smooth and it was tight then this other bit screwed on (like lock nut)i tightene that right up to the bb of the frame nice and tight .coupkle hours later it came loose again .
basically has anyne else had this problem?how do i resolve this .
coupke my ideas are are the screw in cups handed?could they be in the wrong way if so which way shhould they go how to i know this ?

[HEYWOOD BMX]

  Cups are "handed" like pedals but opposite.Looseball Euro bbs are a bloody pain though! Try a bit of Threadlock on the cups..

[MartyC]

Looseball BB's should have a locknut, back one onto tuther should be right  .  Any pics of the setup as would help diagnosis 

[chi11i]

echo Heywood - def handed (as heywood says), def a pain in a*se, def threadlock - lots. what brand? those 4jeri ones? salt rookie? they are all pretty high maintenance.