Error in "activities"

[trivoc]

Hi, i have installed SufarCRM Version 4.5.1e (Build 1049) and all works fine for some weeks, but now when i go to activities i get this error message:

Fatal error: retrieve_parent_fields() [function.require]: Failed opening required '' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/elocome/public_html/crm/data/SugarBean.php on line 2951

SugarBean.php file has 777 permission.

Server information:
mysql 4.1.22
PHP Version 4.4.7
httpd (1.3.37 (Unix))

I'm sorry but i haven't found this kind of error (or similar) in the forum. Does someone knows why it appears and how to solve it?

Thanks in advance.

[trivoc]

Nobody knows? please...