I'm afraid that I have no answer to your specific Ruby issue. The 10.7.4 update to my mini server has had no problems at all (so far :-}).
However, I'm confused by your reference to Security Update 2012-002, which is intended only for machines running Snow Leopard. I would not be surprised if it caused instability when installed on a Lion system. I would have expected the install process to complain that it could not be added to Lion.
As a rule of thumb, I find that updates are less troublesome when using the Combo updater, rather than the basic point release update.
You may need to back out the update (by restoring from Time Machine or other backup), then re-apply the correct (server-specific) upgrade.
Yesterday I applied the latest Lion Server Update to my Mac Mini Server (not sure about the update's number).
I also experienced the "fans blowing full-blast" symptom for no apparent reason (no heavy apps running - Mac almost idle- and CPU, HDD, Network monitors flatlining). As well as a minor issue on the screen-sharing side: it didn't display the initial grey-background login page, but after I logged in blindly it was fine.
The update did a restart but no power-off, so I thought the issues might occur because the hardware hadn't properly reset (yep, I had to use Windows at work...)
Dunno if that was the cause, but after a shutdown, power-off and restart, the symptoms disappeared. Will see... so far so good.