A real creative excuse :

Just added this to my "Reasons for Non Payment" list.

"________ has been greatly affected by SARS. We have not been able to contact our customers as they are all closed.

I think we will not be able to pay on ____. But I will contact my customers when they re-open and will get back to you on when we can make payment to you."

And I thought I've seen everything !

Though the delayed payment hurt, the excuse sure lightened up my day !