Topic: Loading white page-glpi 0.90

Iam using glpi 0.90. I have started the helpdesk functionality from this month onward. Initially every thing was working fine. But now I sees a strange problem. When any of the user try to reset their password using the forgotten password link  they  get a white screen. This was working fine initially. Also the screen becomes white when a user tries to login with a wrong password. Please give any solution to resolve this issue. I increased the memory limit in my php.ini to 256M and restarted httpd. But nothing changed.