FOLLOW UP FROM APPLE
Called apple back - they have provided : a workaround ( not a fix ).
For us this is fantastic
STEPS (***ON THE CLIENT***)
(1) Open the following file : /etc/hostconfig
(2) Change the line SPOTLIGHT=-YES-" to "SPOTLIGHT=-NO-"
(3) Reboot
Spotlight will be disabled however your files should stop vanishing.
Thank you very much apple. We are happy that there is now a workaround
PS : TESTED ON 10.4.5 Client and Server
Upgrading to 10.4.6 Server stopped login working before this
workaround was applied to the clients.
It seems people have had mixed results with the 10.4.6 upgrade.
Be prepared to roll back to 10.4.5 if you are applying this upgrade.
Hope that helps.