To run Crystal Reports from web server the server needs to be able to run 32 bit web application on the SBS/Windows Server 2008/2011 server.
Sometimes this causes compatibility issues the links below have possible solutions.
When Exchange is installed on the same box it configures an RPC HTTP proxy which does not run in 32 bit mode.
The file rpcproxy.dll is a windows system file and we suggest to check these solutions to modify the settings to be able to run 32 bit applications from IIS.
if owa - http://www.mosmar.com.au/chris-blog/2011/3/15/taking-care-of-bitness-or-how-to-run-a-32-bit-app-with-owa-2.html