Intermittent Sieve

[Alex Potter]

I  am using Kolab server 2.2 on a Debian 4.0 machine, 

I am experiencing some oddness with my sieve script whereby it fails to 
deliver incoming mail to the correct folders, but with no consistency. is 
mail destined for a folder sometimes gets there, sometimes not.

Has anyone had similar experiences, or am I just working the poor box too 
hard? It's a 2.3 GHz Celeron with 1GB memory doing nothing else.

Regards

Alex