Hello there.
Leopard and HP 6180 here. Printing works fine with IPhoto8 (and worked fine before with Tiger and '06)
But I ran into the same trouble - several DinA4 (German Letter format) Sheets were wasted trying to get the d*mn printer to use it's 4x6 (=10x15cm's) photo sheets.
It seems to me that one must select the correct Papersize and Layout twice: First in iPhoto, then, a second time, in the print setup dialogue.
With HP, the print setup dialogue is really tricky. Several Menus to plough trough, the most important in this case is the paper handling and quality. Somewhere you can select it.
The problem is: When you set up everything right in iPhoto and click on "print", a new dialogue window opens where you can adjust the HP Settings. Most of the time, this window appears without it's many submenus. But there is a small triangle button which opens a bigger dialogue window. Now there are these maaaany options.
I found out that beneath the correct sheet tray (main or photo tray), there is another menu where you can also select the correct paper format. So: One has to select not only the correct tray, but also the correct format, and this not only in iPhoto, but also in the HP Print Menu.
Isn't this a nuisance? Thank God there's a way to make presets which you can quickselect. Did you know? I learned it the hard way...
Well, after telling both iPhoto and my HP Menu what i want, voilá: There comes the sun! Nice 4x6 High Quality iPhoto Printout. Didn't use the original HP Ink BTW. Spoiled it all trying to get the right setup. Used my sweat instead...
Fox