The problem is not SSRS, the problem is asp runing on 32-64 bits. to enable the SSRS follow these steps:
1. To run the 64-bit version of ASP.NET 2.0, Click Start, click Run, type cmd, and then click OK.
2. Type the following command to disable the 32-bit mode:
cscript %SYSTEMDRIVE%\inetpub\adminscripts\adsutil.vbs SET W3SVC/AppPools/Enable32bitAppOnWin64 0
3. Type the following command to install the version of ASP.NET 2.0 and to install the script maps at the IIS root and under:
4. Make sure that the status of ASP.NET version 2.0.50727 is set to Allowed in the Web service extension list in Internet Information Services Manager.
5. Check the SSRS configuration
Note The build version of ASP.NET 2.0 may differ depending on what the currently released build version is. These steps are for build version 2.0.50727.
view this link : http://support.microsoft.com/kb/894435/en-us