I took the attune gem feat, and can't seem to get it working. I'm playing the OC with a Wizard 5/ EK 4/ Spellsword 5. I've tried various low level spells, mirrow image, protection from evil, ect. I'm using a saphire for this test. I'm 5000 xp over my level, and have 89,000 gp in my bank. When i cast the spell on the gem, i get this message: 'not a valid target for this spell'.
I noticed something in the manuel about a sub-radial entry, but i've checked them all, and can't find one. Thanks for any help.