hibernate - Swap partition does not mount on restart

I am using Ubuntu 12.04 and was trying to enable Hibernate.I came across that one should have Swap Partition equivalent to RAM in system so created one.
My file system information on

sudo fdisk -l /dev/sda

Disk /dev/sda: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders, total 312581808 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000b11e9

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1              63       96389       48163+  de  Dell Utility
/dev/sda2           98304    84097023    41999360   83  Linux

/dev/sda3        84097024   167878655    41890816    7  HPFS/NTFS/exFAT
/dev/sda4       167879311   312575999    72348344+   f  W95 Ext'd (LBA)
/dev/sda5       167879313   287396152    59758420    7  HPFS/NTFS/exFAT
/dev/sda6       287397888   310425599    11513856    7  HPFS/NTFS/exFAT
/dev/sda7       310427648   312575999     1074176   82  Linux swap / Solaris

I am able to hibernate my system once I swapon my /dev/sda7 partition.

For that I do,

mkswap /dev/sda7
and swapon /dev/sda7

I even added entry in /etc/fstab

UUID="xxx" /dev/sda7 none swap sw 0 0

Everything happens successfully including sudo pm-hibernate
But when I restart my system after Hibernate its not able to load my swap partition.

I checked using Gparted Partition Editor then for /dev/sda7 the file system becomes unknown.

Please help in resolving this.