Phplist version 3.2.5, internal error 500 while updating the email field in update preferences page

hii team
I recently clean install phplist to version 3.2.5.
i am getting 500 internal server error, if i update the email address field on the preference update page i.e.
domain/lists/?p=preferences&uid= ( uid of the user).

If i keep intact the email and confirm email address field then the page executes and shows me the confirmation page stating the records have been updated,
But if i change the email field, I get 500 error.

i tried searchin a lot on old as well as new forums but could not find anything relating to PHP-FLAG in .htaccess file in all the directories.
Checked the server’s php.ini, it has magic_quotes_gpc as off.
i also checked the error log which stated that this magic_quotes_gpc = On is no longer in use.

I checked the .htaccess file in all the folders starting the lists/ and looked for the same but no mention of the same. all the directories and the files have correct permissions on the server.