Here's the response I received.
We appreciate your e-mail regarding the security PTSC. I apologize for any confusion in the matter. There are several reasons why E*Trade would prevent people for purchasing certain securities. This could be due to the stock being traded thinly, volatility, and/or recent corporate actions.
This doesn't mean that in the future you won't be able to purchase this security online. If you have anymore questions about trading please let us know at the number below.
If you have anymore questions or concerns about this please feel free to contact us at 1-800- ETRADE 1.
I hope this information has been helpful.
NOT!!!