Sometimes error
 

Some users report me a error when they login.
When they login again or refresh the page the error seems te be over.
This is what they rapport me:

Fatal error: Call to undefined function pp_get_filename() in /home/html/forum/forum.php(654) : eval()'d code on line 186

What can this be?

Your forum code should not be calling photopost functions you sure your not running some unapproved hack in vb?

Yes sure, The last time I don't get any errors more as above.
I wait and see what will happen in the future

yes more than likely a hack mod issue because photopost does not run in your forum files.