Does anyone have a direct link to the Paypal schedule at iStock?  I opened a ticket for payment back on May 12, and 11 days later the ticket is still open and nothing seems to be happening.  I remember the schedule indicating a delay should be expected, but I cannot locate the schedule on iStock to verify if it is time to contact support yet.

you will receive your money on May 25th, if it's not a public holiday in Canada.

You requested payout on Tuesday. Cut-off is monday morning, so you have to wait

I know your question has already been answered, but here's a link to the schedule anyways:
http://www.istockphoto.com/docs/PayoutSchedule_2009.pdf

For PayPal you should make your request before 9am MST (= 4pm GST) on Monday to receive it the following Monday. The only exceptions to this in 2009 are Aug 3, Sep 7, and Oct 12, where Monday is a Canadian holiday and you have until 9am on Tuesday to make your request.