I am using a Canon 9500 series printer with a Mac Mini using Adobe Photoshop Elements 8 and Canon EasyPrint Pro to print a 13 x 19 poster on glossy paper. However when I get to actually printing it, all goes smoothly until I get an error dialogue with the Photoshop logo saying "an error occurred while printing, there may not be enough memory". How can I clear the printers memory (the cache is already empty), and if thats not the problem, what IS the problem, and how can I fix THAT?
The printer's memory should not need to be cleared. It is automatically cleared at the end of each job. In your case (assuming the printer is a Pixma Pro9500) you cannot add any memory either. However, not being a PostScript printer, the Mac driver works via cups and the application sends it PostScript.
I suspect the memory problem is with the Mac, or with PhotoShop. Start by making sure the image is flattened and then try again.