pg_resetxlog says file system is read only?

#postgresql freenode channel directed me to write the hackers list

I have backup files. Version I believe is 7.4.

pg server stopped - short log file is pasted at end of this email

PANIC re checkpoint record seems to indicate running pg_resetxlog

Ran pg_restxlog with -n successfully and it appeared to have numbers
to work with. Then

su postgres
crunch-a:/var/log/postgresql$ /usr/lib/postgresql/bin/pg_resetxlog
/mnt/pgdata/postgres/data
The database server was not shut down cleanly.
Resetting the transaction log may cause data to be lost.
If you want to proceed anyway, use -f to force reset.

crunch-a:/var/log/postgresql$ /usr/lib/postgresql/bin/pg_resetxlog -f
/mnt/pgdata/postgres/data
pg_resetxlog: could not open file
"/mnt/pgdata/postgres/data/pg_xlog/000000AF00000003": Read-only file
system

crunch-a:/var/log/postgresql$ ls -l
/mnt/pgdata/postgres/data/pg_xlog/000000AF00000003
ls: /mnt/pgdata/postgres/data/pg_xlog/000000AF00000003: No such file
or directory

Here is the output of pg_resetxlog -n:

pg_control values:

pg_control version number: 72
Catalog version number: 200310211
Current log file ID: 175
Next log file segment: 2
Latest checkpoint's StartUpID: 60
Latest checkpoint's NextXID: 193187533
Latest checkpoint's NextOID: 17127133
Database block size: 8192
Blocks per segment of large relation: 131072
Maximum length of identifiers: 64
Maximum number of function arguments: 32
Date/time type storage: 64-bit integers
Maximum length of locale name: 128
LC_COLLATE: C
LC_CTYPE: C

Disk does not appear to be full:
df -k
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 35001508 4130476 29093040 13% /
tmpfs 518252 0 518252 0% /dev/shm
/dev/sdb1 70557052 17567256 49405700 27% /mnt/pgdata
/dev/sdc1 8744304 393792 7906320 5% /mnt/pglogs
65.221.104.253:/bak 344620624 264253272 80022736 77% /mnt/bak

Complete log (its very short) from time where pg server quit running:

2005-08-03 08:38:27 [32119] LOG: could not create IPv6 socket:
Address family not supported by protocol
2005-08-03 08:38:27 [32127] LOG: database system was interrupted at
2005-08-03 03:56:54 EDT
2005-08-03 08:38:27 [32127] LOG: could not open file
"/var/lib/postgres/data/pg_xlog/000000AF00000001" (log file 175,
segment 1): No such file or directory
2005-08-03 08:38:27 [32127] LOG: invalid primary checkpoint record
2005-08-03 08:38:27 [32127] LOG: could not open file
"/var/lib/postgres/data/pg_xlog/000000AF00000001" (log file 175,
segment 1): No such file or directory
2005-08-03 08:38:27 [32127] LOG: invalid secondary checkpoint record
2005-08-03 08:38:27 [32127] PANIC: could not locate a valid checkpoint record
2005-08-03 08:38:27 [32119] LOG: startup process (PID 32127) was
terminated by signal 6
2005-08-03 08:38:27 [32119] LOG: aborting startup due to startup
process failure
2005-08-03 10:08:50 [10168] LOG: could not create IPv6 socket:
Address family not supported by protocol
2005-08-03 10:08:50 [10173] LOG: database system was shut down at
2005-08-03 10:05:42 EDT
2005-08-03 10:08:50 [10173] LOG: could not open file
"/var/lib/postgres/data/pg_xlog/000000AF00000003" (log file 175,
segment 3): No such file or directory
2005-08-03 10:08:50 [10173] LOG: invalid primary checkpoint record
2005-08-03 10:08:50 [10173] LOG: invalid secondary checkpoint link in
control file
2005-08-03 10:08:50 [10173] PANIC: could not locate a valid checkpoint record
2005-08-03 10:08:50 [10168] LOG: startup process (PID 10173) was
terminated by signal 6
2005-08-03 10:08:50 [10168] LOG: aborting startup due to startup
process failure