SSRS Report will not run on Sharepont Website

I have a SSRS Report using multi-select parameters.  It will run OK on a SSRS web server.

However, on a Sharepoint with SSRS integration, the SSRS report will not run. After entering the multi-select parameters, there is no processing of the report.

Why would a report run on a SSRS Web server but not a Sharepoint Web Server?

I am using Sharepoint 2010 with SQL 2008 R2 SP2.

Thanks.