Originally Posted by MattP
Unforunately these achievements were not posted to xbox.com when Episode 4 was first released. To resolve this issue, you will need to recover your gamertag and replay Episode 4. I apologize for the inconvenience.
I had the same problem as well. I did as you said, even cleared my Xbox cache, but still nothing unlocked. I got up to the first area where an achievement should be unlocked and still it was shown I only had 32/40 done. Do I have to complete the entire episode over for all to unlock or is there just nothing I could do at this point? That really disappoints me...