This was exactly the problem :)
Thanks to all.

Francoise Becker wrote:
> Make sure you have an "Upload" directory with the correct permissions so that 
> the web user can write to it.
>
> On 18 May 2007 at 13:42, Andrés Guerrero Doblado wrote:
>
>   
>> I am a newbie on Listserv and perhaps my error should be something 
>> stupid, but I can't find the problem.
>> Everything is working perfect, but users can't send messages using the 
>> web interface. When I try to send a new message nothing happens: no 
>> error messages, no feedback messages... just nothing :) I've checked the 
>> logs and nothing appears. Can anybody give me a clue?
>>
>> Thanks in advance.
>>
>> Regards,
>> Andrés Guerreero
>>     
>
>