<UPDATE>8/19/2009
-- Microsoft has informed me that there is a "newer" new build of the SSRS 2008 SP1 CU3 that just came out that remedies this situation (I'll let you know if I find any issues with it):
1. Symptom - Getting error: "Reporting Services Add-in for SharePoint products and technologies is not installed" on installing RB2ClickOnce.msi on Report server .
2. Cause - This is a bug. Unable to install RB2Clickonce.msi (from sp1)
3. Resolution - the x64 RB 2.0 package is available now on the following site:
http://support.microsoft.com/hotfix/KBHotfix.aspx?kbnum=971491&kbln=en-us
If you browse to this site with an x86 browser make sure you click the link that says "Show hotfixes for all platforms and languages (10)" to list the x64 installer.
SQL Server 2008 All (Global) x64 sp1 SQL_Server_2008_SP1_Cumulative_Update_3_RBClickOnc 2008 10.00.2723.00 122186490 8/10/2009 4:40:55 PM
</Update>
After installing and configuring SSRS Integration with SharePoint across my Farm and ensuring that all was working, I perused the log files on my Servers and noted that in the Application Event Log on each of the Front-End Web Servers there were periodic Failures to load an assembly which theoretically should NOT be needed or used:
Error: Failure in loading assembly: Microsoft.ReportingServices.SharePoint.UI.WebParts, Version=9.0.242.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91
In point of fact this DLL is not even loaded on any of the machines (as SQL 2k8 SSRS reporting services uses version 10.0.0.0 instead which is installed…).
I then opened the web.config files for each Front-End Web Server’s Portal Web Application directory (i.e. the default location of which is: C:\inetpub\wwwroot\wss\VirtualDirectories\Web Application Name) where the problem existed and found that BOTH version 9.0.242.0 and version 10.0.0.0 were marked as Safe in the Safe Controls area of the config file. (Note: if you have more than one Web Application that you are using to display SSRS reports you will have this issue in each of those as well).
Snippet from the web.config file:
<SafeControl Assembly="Microsoft.ReportingServices.SharePoint.UI.WebParts, Version=10.0.0.0, Culture=neutral,
PublicKeyToken=89845dcd8080cc91" Namespace="Microsoft.ReportingServices.SharePoint.UI.WebParts" TypeName="*" Safe="True" />
<SafeControl Assembly="Microsoft.ReportingServices.SharePoint.UI.WebParts, Version=9.0.242.0, Culture=neutral,
PublicKeyToken=89845dcd8080cc91" Namespace="Microsoft.ReportingServices.SharePoint.UI.WebParts" TypeName="*" Safe="True" />
Note the one in Yellow (9.0.242.0)… this is what is ultimately causing the Application Event Log error.
To fix this problem all you need do is to comment out or remove the SafeControl Assembly for the 9.0.242.0 entry in EACH Front-End Web Server’s Web Application’s web.config file for each Web Application that has SSRS integration inside of it… e.g.:
<!--SafeControl Assembly="Microsoft.ReportingServices.SharePoint.UI.WebParts, Version=9.0.242.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91" Namespace="Microsoft.ReportingServices.SharePoint.UI.WebParts" TypeName="*" Safe="True" /-->
I have highlighted in RED the additions to this entry to add an XML comment around the entry.
(Note: I personally prefer commenting out this entry as opposed to removing it completely, so that 1) you have a record of this change, and 2) any change you make this way is more easily un-done if need be.)
Hope this helps!