can't swapon second partition after swapoff, overwrite /dev/urandom, swapon

I tried googling and checking docs but couldn't find anything relevant.
I have 2 swap partitions, /dev/sda6, /dev/sda7. 1 GB of Ram
I wanted to wipe my swap partitions, so I did swapoff /dev/sda7, then
dd if=/dev/urandom of=/dev/sda7, then mkswap /dev/sda7, then swapon
/dev/sda7
With swapon /dev/sda7, I get the following error message:
# swapon /dev/sda
swapon: /dev/sda7: Invalid argument

I noticed afterward that mkswap made a swap that was considerably smaller
than the 1 GB allotted to each of the two swap partitions, it was only about
200-250 MB in size, it should have been 996 MB (just under 1 GB formatted)
or so in size. Don't have the error message available. The only google
item I found for this was old info on old pre 2.2 or 2.0 kernels with older
version of swap vs. newer version of swap, with mkswap now defaulting to the
new version so this shouldn't be an issue.

I added the swapfile (/swapfile0) after I had problems with swapon /dev/sda7

I also did a dd if=/dev/zero of=/dev/sda7 to try the whole procedure again
and swapon /dev/sda7 still fails with the same error message. But the
/dev/sda7 partition is now showing the correct size, ie: 1 GB after dd
if=/dev/urandom of=/dev/sda7 or dd if=/dev/zero of=/dev/sda7 is run.

I haven't rebooted yet (I have a lot of apps I don't want to close yet and
the laptop is temporarily serving some web sites). So I don't know if that
will fix things, but I also modified the swapon start up script so it
encrypts the swap partitions with cryptsetup, so I may not be able to
diagnose the problem by rebooting unless I change everything back.
--------------------

Any ideas for what I can do without rebooting would be appreciated, why is
swapon failing with no error messages in /var/log/messages? (or kern.log)
Any help is appreciated.
Diane.

--------------------
I tried fdisk -l and cfdisk
both were segfaulting yesterday, but cfdisk /dev/sda just gave me this:
GNU cfdisk 1.0

ATA Hitachi HTS54161
Disk: /dev/sda Disk type: msdos Size: 160041885695B, 160042MB
Heads: 255 Sectors per track: 63 Cylinders: 19457

Number Flags Part Type Filesystem Label Size
------------------------------------------------------------------------------------------
None Free
space 1.02MB
1 Primary
ntfs 1573MB
2 Bootable Primary
ntfs 75000MB
None Free
space 3.44MB
3 Primary
reiserfs 28994MB
4
Extended 53497MB
5 Logical
reiserfs 24997MB
6 Logical
linux-swap 1003MB
7 Logical
linux-swap 1003MB
8 Logical
[Linux] 17997MB
9 Logical
fat32 8497MB
None Free
space 971MB
------------------------------------------------------------------------------------------
fdisk is still segfaulting:
# fdisk -l /dev/sda

Disk /dev/sda: 160 GB, 160039272960 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
Segmentation fault

---------------------------
Debian Etch,
2.6.22-4-amd64 #1 SMP Tue Feb 12 10:29:27 UTC 2008 x86_64 GNU/Linux
Toshiba A215-S7422 laptop
---------------------------

$ cat /etc/fstab
# /etc/fstab: static file system information.
#
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
/dev/sda1 /vistaback ntfs 0 0
/dev/sda2 /vista ntfs 0 0
/dev/sda3 / reiserfs notail,noatime 0 1
/dev/sda9 /fat32windows vfat defaults 0 0
/dev/sda5 /home reiserfs notail,noatime 0 2
/dev/sda6 none swap sw 0 0
/dev/sda7 none swap sw 0 0
/dev/hda /media/cdrom0 udf,iso9660 user,noauto 0 0
/swapfile0 swap swap defaults 0 0
----------------------------
# cat /proc/swaps
Filename Type Size Used
Priority
/dev/sda6 partition 979924 711140 -1
/swapfile0 file 1048568 0 -4
------------------------------------------------------------------------------
# free
total used free shared buffers cached
Mem: 899024 888660 10364 0 53996 138940
-/+ buffers/cache: 695724 203300
Swap: 2028492 711140 1317352


Any other info needed?

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