Weird. It's a new chain too? If you take a ruler to the center of one link, the 12" mark should hit less than 1/8" away from the center of a pin 24 links away. If it's a brand new ring and a slightly stretched chain that might do it too.

I don't think the ring would be too wide, 9 speed era chainrings work fine with 10 speed chains.

You're sure it's not a little bit of FD rub?