Blank page with include

[Punchak]

Hi folks,

I've tried to upgrade my board to v3.5, everything is fine except if I use plugin system ton include some file, it generate a blank page.
For exemple :

ob_start();
require("path/file.htm");
$random_tips = ob_get_contents();
ob_end_clean();

The syntax is correct, the path ok, file is a flat html file. If I disable this plugin (hook global_start) everything is ok.

What's wrong ?

Thanks for your help ;)