pcuaron on "Attempting to update plugins results in 503 error after several minutes"

Hello. I'm using wp 3.4.2 on a hosting service. I can access the ftp server and make changes using a ftp client (ie I have the correct credentials).

When I try to update a plugin using the admin dashbord, after clicking "update now", the page keeps loading for several (at least 5) minutes. Afterwards I get a "Error 503 Service Unavailable" error. FTP settings are hardcoded in wp-config.php. This happens with all the plugins. wp-content has, afaik, the correct permissions set.

Any idea what could be happening?

Thanks!!