Sorry I don't have an answer for you but I remember a year or so ago people were having the same problem with Danby kegerators. There was a fix that you can do yourself. I've been trying to find on Google. I know you don't have a Danby but I'll bet the same fix will help yours. It is basically making an adjustment (internally) on the thermostat. Somebody here will surely know. I'll keep looking.
I've been manually adjusting it but I haven't gotten it any colder yet. How much should I turn the screw? A 1/4 turn? Thanks for the thread it really helped out.