AT&T Uverse IPv6 vs. Mac OS X 10.(old)

(Apologies in advance to non-Apple users) Mac folks, Last week AT&T ?upgraded? our Uverse service. All of our Macs running anything 10.6.8 or older quit working. Cure was to turn off IPv6: System Preferences -> Network -> Advanced -> TCP/IP -> iPv6 to ?Off? instead of ?Automatic?. Symptoms were *very* widespread, and matched reasonably well to failing hard drive or failing memory - system freeze, spinning beach-ball forever, can?t read directory, etc. etc. etc. On the G3, I rebooted in single-user mode and actually got part way through the output of ?ps -aux? in one case before freezing. However it did respond to Ctl-C and would then do a ?ps -a? no problem, just no ?ps -aux?. We were a bit silly, didn?t read our Uverse email, and didn?t test other systems before hooking more old systems into the network - which then didn?t work. We were panicing about viruses, pulling hair out, sacrificing goats ... Systems affected were : iMac G3 Mac OS X 10.4.11 - ethernet PowerBook G4 Mac OS X 10.4.11 - wi-fi iMac 2011 intel Mac OS X 10.6.8 - wi-fi Apologies if this is a known bug, but it really puzzled us for a while because the effects were so systemic; I hope I can prevent anybody else from getting a nice new (needless) hard drive like the 2011 iMac did? - Mark 210-522-6025 office 210-379-4635 cell