I have 2821 routers at 2 sites running EBGP with service providers, and IBGP to each other. The 2821s run OSPF as an IGP and are connected to ASA5520 firewalls, and to each other. The 2821s are in area 0, with one site being area 1 and the other area 2. The ISPs are sending a default route as well as the full BGP table. Default information originate is used in OSPF at both sites to inject the BGP learned default route.
Yesterday we had an ASA crash and reload at one of the sites. It came up with a new router ID and was not passing routes inside or outside until we cleared the OSPF processes on the adjacent routers. Even then the default route was absent. Looked at the OSPF database in the 2821s and 0.0.0.0 was not there. A sh ip route 0.0.0.0 showed the BGP route as expected. I tried various clear commands, but finally just added always to the default information originate, and the default showed up in OSPF.
I am perplexed. This has worked fine for over a year. Dug into the books, and can find no other requirement for default information originate except for 0.0.0.0 to be in the route table, which it is.