I have a page for upload files, In .htaccess
file I have this:
php_value upload_max_filesize 40M
php_value post_max_size 40M
I
As far as I can tell, you're probably exhausting the memory_limit of PHP, that is, PHP is trying to allocate an amount of memory greater that the memory_limit param value.
Maybe you're uncompressing the image on the fly or copying some data that needs too much memory to be allocated, try increasing that limit.