i'm running iFolder 2.1.7 on NetWare 6.5 SP5

I have all my user organized in one OU. If i try to change the iFolder Ouota on some user i get this error message on the web site:

modifyObject: Type or value exists
distinguished name: cn=peter,ou=user,o=customer
objectClass: iFolderUser
attribute: iFolderQuota

The dstrace screen with the option +ldap show me this error message:
Sending search result entry "cn=peter,ou=user,o=customer to connection 0x8f295ee0
Searching "": NDS error:fatal (-699) returned
LDAPSearchtoCB failed, err = fatal (-699)
Sending operation result 80:"":"NDS error:fatal (-699)" to connection 0x8f295ee0

iFolder is searching in the right container and i didn't get this error message with every user in this context.
If i check the quota settings after this error message on the user. the other tab shows me the correct new value, but the ifolder client shows me the old value

I have also reinstalled ifolder and updated to SP5 but nothing has changed

Are there any tips for me to solve this problem???