I've noticed subtle differences in execing a batch file on MS Windows with or without prepending the call with the command interpreter, cmd.exe. Here's an example:

(Eigene) 1 % cd c:/iskv/portal_1024
couldn't change working directory to "c:/iskv/portal_1024": no such file or directory
(portal_01024) 2 % cd c:/iskv/portal_01024
(portal_01024) 3 % glob *
config cti dist help resource resource_cti start_portal.bat
(portal_01024) 4 % exec -- start_portal.bat
Unable to access jarfile c:\iskv\21c_winbk_\bin\csvstart.jar
Das System kann den angegebenen Pfad nicht finden.
(portal_01024) 5 % exec -- cmd.exe /c start_portal.bat
(portal_01024) 6 % exec -- cmd.exe /c start_portal.bat &
4660
(portal_01024) 7 % exec -- [auto_execok start_portal.bat]
Unable to access jarfile c:\iskv\21c_winbk_\bin\csvstart.jar
Das System kann den angegebenen Pfad nicht finden.
(portal_01024) 8 % 

Don't know what's going on yet.