No oil pressure at startup - filter?

I changed my oil last weekend, and now everytime I start the engine the oil pressure light stays on for a few seconds. I'm wondering if it might be because of the Fram PH8A filter I used. I have the right angle adapter and the filter is sitting almost perfectly horizontal. I thought this filter was supposed to have an anti-drainback valve, so this shouldn't be happening... right? What oil filter do you guys use? Anyone else have this problem?