Okay, let me see if I follow so far:
I've got about 20 Macs ....
..... My two or three Tiger machines could download all of the updates except for the iChat update. I have one laptop left to do that's running Tiger and it just refuses to download anything......
Okay so this is an office network with 20 Macs, give or take. Two or 3 of these are running Tiger. What version of Tiger is this machine running? (.4, .6, .8)
What operating system is on the other machines and what versions are they running? (10.2.x, 10.3.x, 10.4.x)
.....I tried running the updates and they all failed. ......
You tried to download the updates and
all of the machines failed to get the udpates, or did
all of the updatesfail on certain machines?
If it is select machines that failed either in part or all of the updates, have you tried running some other utility like MacJanitor, OnyX, or MainMenu to clear out system caches on those systems? I ask again because Disk Repair and Permissions Repair will not do this, and it wasn't clear from your response whether or not you cleared out system cache using some other method.
.....Last time I ran the updates w/o problems was months ago (I don't update the Macs often)
So the updates have worked in the past, again confiming that it isn't an issue with the Software Update not doing its job. It comes back on the connection.
connecting to two T1's through an isa server.
Has there been any change to any firewalls? What kind of authentication method is used on the server? Have you tried clearing the server cache?