MTU discovery problems in the Internet?

All, In the last few days I have noticed two sites, quite by accident, to which MTU discovery does not work correctly. In one case the router which failed blackholed the traffic, and in the other case, the router returned an MTU value which is garbage (Friday I got 18K, today I get 63692!) Many sites depend on MTU discovery working properly, and the need for MTU discovery is not going away! I ask all of you provider types out there to please look over RFC1191 (it is short). If you don't have tools to diagnose MTU discovery problems, you can pull down ftp://ftp.psc.edu/pub/net_tools/traceroute.tar which includes a -M switch for MTU discovery. Thanks, --Jamshid