We got puzzled with some nice error when opening the reports. We had nice two server setup with application server (ms crm) en database server (sql & reporting server). Changes all things for trust for delegation on install/service account level, unfortunately we still got 401.1 error e.g. http unauthorised.
The trick was in the kerberos authentication, you should add dword to registy (hkey_local_machine/software/microsoft/mscrm/... add NTLMForSQLRSServer with value 1 and everything started to work.
So just follow these steps:
1. On the Microsoft Dynamics CRM server, click Start, click Run, type regedit , and then click OK.
2. Open the following registry key: HKLM\Software\Microsoft\MSCRM
3. Right-click MSCRM, point to New, and then click DWORD value.
4. Type NTLMForSQLRSServer .
5. Double-click NTLMForSQLRSServer , type 1 , and then click OK.
So maybe this will also help also in your case, but yet you know what I gonna say.... no guarantees