As you've posted in the General section and not stated what version of SecurityCenter you have, not too sure here.
In any case, the ability to overlook a file or folder is not possible in the consumer versions but is a feature we have repeatedly asked them to reintroduce.
There's a rumour that it may happen in the 2011 product coming out later this year.
It may interest you to try the beta product, but wait awhile as it isn't yet a feature.
(The current beta is the same as what's in production - new version should appear sometime in the fall).