Index problem in EV 10

Hello,

I've a new EV 10.0.4.1333 install on a Windows 2012 server.

I archived some mailboxes and everything seems ok, but I'm unable to search archived items: "Failed to perform the search request".

I'm able to successfully synchronize and rebuild indexes, but the verification fails : "The verify subtask has failed: Failed to search the index volume.Access is denied.  (0x80070005)"

A dtrace shows access denied errors:

166    13:17:28.905     [160]    (EVIndexVerifyTask)    <5948>    EV:L    WinHttpRequest::OnCallback. WINHTTP_CALLBACK_STATUS_HEADERS_AVAILABLE.
167    13:17:28.905     [160]    (EVIndexVerifyTask)    <5948>    EV:L    WinHttpRequest::OnCallback. WINHTTP_CALLBACK_STATUS_HEADERS_AVAILABLE. Status code=403
168    13:17:28.905     [160]    (EVIndexVerifyTask)    <5948>    EV:H    WinHttpRequest::OnCallback. HTTP request returned 'access denied' or 'forbidden'.  Is the service running?
169    13:17:28.905     [160]    (EVIndexVerifyTask)    <5948>    EV:H    WinHttpRequest::OnCallback exit. ERROR HR=0x80070005.
170    13:17:28.905     [160]    (EVIndexVerifyTask)    <5948>    EV:M    WinHttpRequest::Callback from WinHttp. pRequest->OnCallback failed with HR=0x80070005. Calling pRequest->OnResponseComplete.
171    13:17:28.905     [160]    (EVIndexVerifyTask)    <5948>    EV:M    IndexQueryServerRequest: OnResponseComplete - HR=Access is denied.  (0x80070005)
172    13:17:28.905     [160]    (EVIndexVerifyTask)    <7128>    EV:L    IndexQueryServerRequest: WaitForSingleObject returned 0.
173    13:17:28.905     [160]    (EVIndexVerifyTask)    <7128>    EV:M    Response received. Result = Access is denied.  (0x80070005), Status = 403
174    13:17:28.905     [160]    (EVIndexVerifyTask)    <7128>    EV:H    CIndexQueryServerSearch::Search2. Request FAILED HR=0x80070005.
175    13:17:28.905     [160]    (EVIndexVerifyTask)    <7128>    EV:L    WinHttpRequest::Shutdown entry. Closing Winhttp handle
176    13:17:28.905     [160]    (EVIndexVerifyTask)    <7128>    EV:L    WinHttpHandle: Closing handle.

Event viewer shows the following error:

Event ID 7182

Index Search failed: Unspecified error  (0x80004005)  
Index: 100AE04DE619AE64E8CC252A24530ED081110000luenparchexc/VolumeSet:16 
Internal reference: SRCI 

It also seems tha the IIS log has unexpected entries.

I checked the IIS authentication but I don't find out what's going wrong.

Is someone has some suggestions, they are welcome.

Thanks!