"invalid request: LDAP schema violation:" when setting domain default COS.

[k1e0x]

When changing a domains default COS, I get.

"Message: invalid request: LDAP schema violation: [LDAP: error code 65 - attribute 'zimbraZimletAvailableZimlets' not allowed] Error code: service.INVALID_REQUEST Method: ZaDomainController.prototype.saveChangesCallback Details:soap:Sender"

What does this mean and how do I get rid of it?

Related, but unanswered post.
http://www.zimbra.com/forums/install...olation%3A

[k1e0x]

did a..

zmprov md example.com zimbraZimletDomainAvailableZimlets ""

and the error went away.. however the users are not picking up changes in either the new cos, or the old one.

Update: never mind, reload fixed this. It's working properly now. What causes this error?