"disconnected from the lobby server"

[ynot]

Try this for a quick fix and see how it goes.

Try a wired connection if you have not done so already.

Switch your DNS servers on the PS3 to one of the following:

Google DNS Servers:
Primary 8.8.8.8
Secondary 8.8.4.4

or

OpenDNS
Primary 208.67.222.222
Secondary 208.67.220.220

Switching to Google's here in San Antonio, TX seems to have helped.

I seldom get disconnects anymore.

SONY also recommends the following:

Troubleshoot Wireless Network Connection:
https://support.us.playstation.com/app/answers/detail/a_id/280/kw/connection issues


Troubleshoot Wired Network Connection Problem on PS3
https://support.us.playstation.com/app/answers/detail/a_id/285/kw/connection issues



Google DNS Could Speed Up Online Games:
http://www.joystickdivision.com/2009/12/google_dns_speed_online_games.php


Hope some of this helps you out.