i did it after your mail.. but after the change (i mean adding the suffix) to the subdomain line, a blank page comes when i enter my master page. both backend and frontend..

You probably did a syntax error

yes u are right. i corrected it. and now the page comes, but same as before.

i also did not understand why it automatically logs out from them master site when i visit subdomain.

All I know for the moment is that you have a problem of permission with your MySQL user and I try to give you a workarround to provide the result of a computation of JMS in hope that would solve the issue temporarly.

This customer had a problem with the setup of his hosting provider that does not allow retoriing correctly the sesssion information between sub-domain.
With JMS 1.2.7, we have now implemented a rescue algorithm that is able to restore the session event when the hosting provider does not do it.
This should solve the case where the sessions are not restored by the hosting server on the same domain.

We can also report that facebook communication is also working correctly with JomSocial and in case of problem of error on session, you have to check the "base domain" in the facebook application to ensure that it is allowed to communicated with the different sub-domain of a given website.

yes, everything is ok with the new version.

thank you for the support.