i get this error "invalid memory alloc request size 18446744072635840654. SQL Status:XX000" when i want to create an index.

The Table looks like this:

CREATE TABLE schema.tblname
(
  id bigint NOT NULL DEFAULT nextval(('schema.tblname_id_seq'::text)::regclass),
  column_1 integer,
  column_2 character varying(20),
  ... 8 other columns ...,
  CONSTRAINT tblname_pkey PRIMARY KEY (id),
  CONSTRAINT tlbname_fk FOREIGN KEY (column_1)
      REFERENCES schema.tblname2 (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION
)
WITH (
  OIDS=FALSE
);

Server version:

PostgreSQL 8.3.8 on x86_64-pc-linux-gnu, compiled by GCC cc (GCC) 4.2.4 (Ubuntu 4.2.4-1ubuntu3)

Hardware (Virtual Machine):

4 Cores, 16GB RAM, 700GB SAN HDD

ulimit -a:

core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 139264
max locked memory       (kbytes, -l) 32
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 139264
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

The History:
We had a crash of the Raid-Controller in the SAN. The redundant Server/SAN prevented a failure of the DB but we had corrupted data in the table.
Then i have searched the table for corrupted data and deleted the rows from the table. Now i want to recreate the index to be sure to have a correct index.

I wanted to create following index:

CREATE INDEX tlbname_column1_column2x
  ON schema.tlbname
  USING btree
  (column_1, column_2);

This was not possible because the following error occurred:

index row requires 2286728 bytes, maximum size is 8191

So i made an index on column_1, this worked fine and deleted it after that.
Then i tried to create an index on column_2 and the error "index row requires 2286728 bytes, maximum size is 8191" occurred.
I searched the table for rows where the octet_length was greater then 20 (because of charvar 20 on column_2) and deletet the lines (approx. 40k rows).

Now when i try to create the index on column_2 it fails with the error "invalid memory alloc request size 18446744072635840654. SQL Status:XX000"

Table info:

rows in the table: aprrox. 1.841.170.000
tablesize: 197GB

The index

CREATE INDEX tlbname_column1_column2x
  ON schema.tlbname
  USING btree
  (column_1, column_2);

already exists since the creation of the table and it worked without any problems. But the recreation does not work.

Any suggestions what i can try or do?
Thanks.