Initially hibernate/resume was working fine. But now system hibernate but doesn't resume, instead it boot-up normally. I had checked SWAP is mounted on /dev/sda2

I have tried hibernate from [menu] -> Leave -> Save to disk
There is no problem in hibernate process, but resume fails.

I have also installed uswsusp package and tried to hibernate through command "s2disk", again it hibernate properly but fail to resume.

Is there any thing to check?