From the IOS 12.0 Network Protocols Command Reference, Part 1, OSPF section concering the
address-summary command:
"For OSPF, this command summarizes only routes from other routing protocols that are being
redistributed into OSPF."
Basically the summary-address command will not summarize OSPF routes. If possible, perhaps you can
create static routes to the 10.1.1.0/24 and 10.1.2.0/24 networks pointing to the null0 interface
and redistribute these static routes into IGRP. Note: if you have additional static routes configured,
you may need to use route maps to control what static routes get distributed into each routing
protocol.