[imp] Problems sending attachments

[Antonio Guerrieri]

Hi all,
with my linux box I can't send attachements with imp.
The file is correctly uploaded but I receive an attachement of (always) 
0 bytes
if it is greater than 1MB.
With a file of 2MB I get a blank page without errors.
horde.log doesn't contain anything about.
php.ini is configured to allow uploads of 20MB (upload_max_filesize) 
and also the mailer.
With the previous version of imp and horde I hadn't these problems.
I have googled but found anything useful...
Any idea?

RedHat 9
Apache 2.0.47
PHP 4.3.3
Horde 2.2.4
Imp 3.2.2

tnx

Antonio

p.s. squirrelmail works well with the same apache and php configuration.