Cannot drop role

I've seen one or two mentions of this problem with no applicable solution.
I have a case where I cannot drop a role because "...5 objects depend on
it" (according to pgAdmin 3). When I connect to the database that holds
those objects (they are not named) and try to drop the role I get an error
message:

[Error Code: 0, SQL State: XX000] ERROR: could not find tuple for
default ACL 2243075

Even after trying a number of queries that are purported to list grants
and ownerships for given ids I can turn up nothing that references the
role by name.

At this point I suspect there's something corrupted in the system catalog.
How can I find the table entry (or entries) that reference that
identifier? The fact that the message is issued suggests a link somewhere
but I cannot locate it.

Many thanks!

Steve

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