unexpected data beyond EOF and character encoding

I'm doing dry runs to migrate my database from 8.1.3 to 8.2.3, with
pg_dumpall | gg_restore, using the executables from 8.2.3.
I'm seeing these messages

ERROR: unexpected data beyond EOF in block 4506 of relation
"coverage_test_val"
HINT: This has been seen to occur with buggy kernels; consider updating
your system.
CONTEXT: COPY coverage_test_val, line 378036: "533359 61566
2007-02-01 DELINQUENCY6 16 0.356509255634 0.5 7"
ERROR: unexpected data beyond EOF in block 414 of relation "rating"
HINT: This has been seen to occur with buggy kernels; consider updating
your system.
CONTEXT: COPY rating, line 56387: "840942 19548 2005-10-25
1 25 \N 1 \N"

The migration otherwise finishes successfully, but those two tables with
the EOF problem have count(*) = 0.

Can this really be a buggy kernel? Is there a list of known Linux
releases that are buggy? Of course, upgrading the kernel on a production
machine is the last thing I want to try...
And here's a theory: a while ago, someone installed pl/R on the database
to do statistics. Executing some pl/R functions would produce a crash of
all the connected clients, and I'd see "unexpected EOF" messages. I
immediately said we needed pl/R uninstalled, and the crashes stopped.
The encoding of my database is SQL_ASCII, which from what I've been
reading, is a non-encoding and will not perform any validation. Would it
be possible that some invalid characters crept into tables related to
those pl/R crashes? Would porting to UTF8 fix this?

Is there a way I can fix those two cases of unexpected EOF so I can at
least perform the upgrade?

Thank you,
Jaime

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