Execute Permission Denied on Stored Procedure using Microsoft JDBC Driver and Windows Authentication

I have a Microsoft SQL Server database that I use Stored Procedures to read/write data to through a Integration Engine in this case InterSystem IRIS. Originally I was using a local server user to do the execution, but for security purposes it was requested that I start using an Active Directory/Windows Authentication user instead. At the time I could not get this to work with the Microsoft JDBC driver since we were running the Integration Engine on a Unix/Linux platform at the time was AIX, but now Red Hat. I was able to use the jTDS JDBC driver to connect to MS SQL without issues as the Active Directory Service Account using Windows Authentication to do the read/writes to MS SQL from InterSystems. But when moving to Red Hat we discovered an issue with the jTDS driver not reusing existing JDBC connection strings, causing massive amounts of connections to be made. So it was suggested that we move back to use the MS JDBC Driver. However I am running into a problem.. I am receiving an EXECUTE permission denied when trying to execute the store procedure. The user and the stored procedure have the correct permissions, however using the Microsoft JDBC driver I get this error. I am using the following format for the connection string... Url: jdbc:sqlserver://host:1433;authenticationScheme=NTLM;integratedSecurity=true;domain=myDomain Does anyone have any ideas on why the stored procedure will not execute with Microsoft's JDBC driver but will with jTDS?