Error 25151. Configuring MOM database failed. Error Code: –2147023564 when installing SCOM R2 Reporting component

Got this error message today at a customers site where a total reinstall of the SCOM R2 Reporting component was at order. The wizard completed almost successfully but then this message popped up:

Hmm. Time for some investigation. This was shown in the log while searching for value 3:
MSI (s) (B4!0C) [13:33:18:838]: Product: System Center Operations Manager 2007 R2 Reporting Server -- Error 25151.Configuring MOM database failed. Error Code: -2147023564 (No mapping between account names and security IDs was done.).

The related accounts were OK, had enough permissions: within SCOM, SQL and on the related servers. To make it more interesting, it is a split installation: the Data Warehouse database resides on another server than the SQL Reporting Server Services (SSRS) instance. Which can be a challenge.

The AD servers were running smoothly as well, no issues there. The accounts were OK, and not locked. So what else could be the matter here?

Time to go through the installation log again. And now more detailed.

Before I could run the reinstall of the Reporting Component I had to revive SSRS first which took me some time. Also I needed to change some credentials for which I used the format <domain name>\<account>. In SSRS this is a valid format. But NOT in the wizard for the installation for the SCOM Reporting component.

And that is what I did.

I entered for the account the credentials in the format <domain name>\<account> instead of <account>. Since there is already a field in place displaying the domain where the account resides the format <domain name>\<account> isn’t needed . Where in other applications that field gets grayed out when the <domain name>\<account> format is being used, but not here in this wizard.

So the installation log told me that it was unable to validate the accounts with the format <domain name>\<domain name>\<account>. Which is normal! Look here:
AddPrivilegeToAccount: Giving privilege to account. DOMAIN\domain\account
AddPrivilegeToAccount: LookupAccountName failed. Error Code: 0x80070534.

So I ran the installation again and now I provided the account name without the domain name as prefix. And all ran just fine…