Hi Mike

What version of SQL Server are you using?

What I would do in this situation is actually look at the string being passed to the cmdshell by adding a select after you have created the DTEXEC command to show the exact string you are asking SQL to execute. I don't think you are passing the command in the following format

EXEC xp_cmdshell 'DTEXEC Command'.

First eliminate the syntax as a problem, then we can begin to work on the rest of the possible issues.