Teradata SQL Assistant 13 on Windows 7 machine

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Teradata SQL Assistant 13 on Windows 7 machine

Hi all,
I installed Teradata SQL Assistant 13 on my windows 7 machine, but I can only execute one query.
After the first query is done, I can't ever execute another query.
All I can do is shut it down and run another Taredata SQL Assistant.

Does anyone know how to solve this problem?
thanks