Themes are "not responding"

[AC Question]

HELP!! i downloaded a theme called "mystery kiss", i decided i didnt like it and proceeded to download another and came up with the error "unfortunately themes has stopped" i reset the phone and carried on trying to change it, but no matter what them i pick it stays with the defaults of mystery kiss and WONT LET ME DELETE it. I reset back to default settings, and its still there. I am trying to avoid factor resetting the phone. Any one have any ideas!?