Running a batch file from a program is a strange idea and pretty much useless: there are many other way to integrate software or make codes pluggable.
So, I never tried it. But few seconds ago I tried, out of curiosity:
System.Diagnostics.Process.Start("mybatch.bat");
Note, I didn't even run "CMD.EXE" with the batch file as a parameter, I tried to start batch file itself (I thought this could be a problem). It worked immediately. Needless to say, I had my executable and the batch file in same directory (see Dave's comment). Did you?
—SA