Preference file squirrelmail could not opened

This morning while trying to login SquirrelMail on my server I got the error like this “ Preference file, /var/www/html/squirrelmail/data/bikram.pref, could not be opened”. I have installed qmail on my mail server and for webmail I have installed SquirrelMail on centos 5.5. I went through the log but error log file is not throwing any type of error. Then I check the permission of the data folder and tally with another server. It seems that there was wrong in the permission of the folder. I then changed the permission of the folder “data” to 755, it works fine now. To change the permission I did, [root@system webmail]# chmod -R 755 data/