imac g5 "cannot connect to update server"

I have an old imac G5 that was given to me and I am trying to get it up and running for students to use, since we are really short on technologyat our broke *** school. The problem is that ther person that gave it to me wiped it almost clean (including the microsoft office). I got a copy of office 2004 and loaded it and it seems to be working.

Unfortunately, I can't seem to get any updates and the internet keeps encountering a problem and closing unexpectedly. Everytime I try to check for updates by going through system preferences or by clicking on the apple and going to "Software Updates" it tells me that it encountered an error or that "cannot connect to update server. When i look at installed updates, it only shows two dates when updates were downloaded (Feb 20, 2012 and August 4, 2011). That doesnt seem right. I have already spent hours that I dont have trying to figure this out. Can anyone help me?