Panic error on attempted update

One of the servers I am responsible for maintaining was apparently having problems earlier today. The servers are all running SuSE 9.2, Apache 2 (not sure what version), and Postgres 8.1.4. Our main server is running Slony 1.1, I think, creating Log-Shipping records that the rest of the servers are then updated off of by means of an hourly cron script.

When I went into the server to take a look at the cause of the problems, I noticed that there were numerous copies of the updating cron script running, all of them trying to do a select on that server's local database. (There was a VACUUM command running at the same time; I do not know whether that had anything to do with this or not.)

I disabled the script so it wouldn't be able to run again and create more overhead to deal with, then attempted to let the backlogged copies finish. They have since dissappeared, but attempting to run the script manually produces the following error messages:

slony1_log_1_00000000000003476171.sql
ERROR: Slony-I: set 11 is on sync 3475773, this archive log expects 3476170
ERROR: current transaction is aborted, commands ignored until end of transaction block
...
...
ERROR: current transaction is aborted, commands ignored until end of transaction block
PANIC: right sibling's left-link doesn't match
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
connection to server was lost

Any clue what's causing the panic message to occur? I understand the aborted transactions, since I'm giving it archive logs later than the one it expects, but I have no clue why I'm getting the Panic call, nor do I understand what it means completely. Would someone please explain to me?

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