warning: in_array() in filefield.module

I add a field in page type, when I try to create a page to test if it work, it shows a warning message:

"warning: in_array() [function.in-array]: Wrong datatype for second argument in C:\Program Files\EasyPHP 2.0b1\www\drupal6\modules\filefield\filefield.module on line 289"

Are there any error? Please help. Thanks