could not open session

[yellowdog-general@lists.terrasoftsolutions.com]

There is a strange problem with YDL 2.3. When i try
to switch user to postgres in a kde terminal:

su postgres

bash give me this error: could not open session

the same thing happens with mysql user.

May be i'm doing something wrong but don't see.

Some help?

Thanks.

Pietro Pesci-Feltri C.