Recently, I failed to install Microsoft SQL Server 2005 Reporting Services Add-in for Microsoft SharePoint Technologies. I tried after server reboot and iisreset but I could not get it to work. This bothered me a lot because I thought I was very familiar and confident with SharePoint Integrated Mode and I have run numerous installations and setups successfully in the past. First thing I did was to look at the installation log file. It is located at C:\Documents and Settings\<USER NAME>\Local Settings\Temp folder of the server you're running the installation on. The log file starts with RS_SP_0.log and the number in this filename will increment as you attempt to install more than once.

Looking at the log file, I found my error:

Calling HCInstal for lcid '1043'

   Outcome code is: 256

Install error: C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\bin\hcinstal.exe return error code: 8

Also, I found this line at the end of the log file:

SSRSCustomActionError: C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\bin\hcinstal.exe return error code: 8

As soon as I got this error, I started to look for what the error code 8 means. Unfortunately, I could not find anything that talks about the error code. Well, I knew that LCID '1043' indicates Dutch (Netherlands) and "hcinstal.exe" is successfully installed on other LCID's. So, the next thing I did was to "pause" all web applications in IIS manager and ran the same installation and finally, I could install the add-in. I still do not know what the exactly problem is but I think it is related to any SharePoint site running that prevents this installation. Good luck!