SS IP7000 Corporate Directory: No response when closing and opening again the directory.

Okay, so I thought I had this solved, but apparently not.

On my SoundStation IP7000 I got a running Corporate Directory. Which is an OpenLDAP-Server with like 5000 entries.

Everything works fine. But sometimes, when I close the phonebook and open it again, the display only shows "Searching ...". 

In the LDAP-Log I can see, that there are no packets send from the phone to the server. But I noticed an established TCP-connection which may have not been closed properly.

When I manually kill this TCP-connection it doesn't work. I think its just closed on the server-side and not on the client.

After a reboot it works fine for some time, but then again there is just "Searching ...", when you close and open it in some cases.

Here is my LDAP-config:

<LDAP><WEB	feature.corporateDirectory.enabled="1"
		dir.corp.address="X.X.X.X"
		dir.corp.autoQuerySubmitTimeout="1"
		dir.corp.backGroundSync="0"
		dir.corp.baseDN="ou=test,dc=polycomldap,dc=com"
		dir.corp.cacheSize="256"
		dir.corp.filterPrefix=""
		dir.corp.pageSize="64"
		dir.corp.port="389"
		dir.corp.scope="sub"
		dir.corp.transport="TCP"
		dir.corp.user="uid=polycom,ou=test,dc=polycomldap,dc=com"
		dir.corp.password="test6"
		dir.corp.viewPersistence="0"
		dir.corp.vlv.allow="1"
		dir.corp.vlv.sortOrder="sn givenName telephoneNumber"
		dir.corp.attribute.1.filter=""
		dir.corp.attribute.2.filter=""
		dir.corp.attribute.3.filter=""
		dir.corp.attribute.4.filter=""
		dir.corp.attribute.1.label="last name"
		dir.corp.attribute.2.label="first name"
		dir.corp.attribute.3.label="phone number"
		dir.corp.attribute.4.label="company name"
		dir.corp.attribute.1.name="sn"
		dir.corp.attribute.2.name="givenName"
		dir.corp.attribute.3.name="telephoneNumber"
		dir.corp.attribute.4.name="o"
		dir.corp.attribute.1.searchable="1"
		dir.corp.attribute.2.searchable="1"
		dir.corp.attribute.3.searchable="0"
		dir.corp.attribute.4.searchable="1"
		dir.corp.attribute.1.sticky="0"
		dir.corp.attribute.2.sticky="0"
		dir.corp.attribute.3.sticky="0"
		dir.corp.attribute.4.sticky="0"
		dir.corp.attribute.1.type="last_name"
		dir.corp.attribute.2.type="first_name"
		dir.corp.attribute.3.type="phone_number"
		dir.corp.attribute.4.type="other" /></LDAP>

Any experiences concerning this issue?