Windows 2008 freezes on copying files

Hi Guys,

Not sure if this is a Hardware or Software problem, but here's the story:

Our Backup server has Wind 2008 R2 instaleld on it , along with Backupexec 2012. It has 8gb ram and was working fine and dandy for the past few months.
One of our users lost all his contacts and calendar on Exchange, while restoring it, the server freezes , only a cold boot would work.

I tried to repeat, I tried to restore from a remote admin console, nothing worked.

I then tried to copy the backup files to another server and installa backup exec there , but just by initiating the copy , 5 or 6 mb would be copied then it freezes.

I tried format/reinstall windows , i even tried with a different hard drive for OS , did the exact same thing. I even tried to copy from a different drive , using the new OS drive, same thing.

Any ideas on what could be causing this? very frustrating... especially that now we cannot reach our backup server... our whole infra is now vulnerable I feel...

The reason why I doubt it's hardware is because of new disk and yet same problem.

I am doubting CPU , because RAM would not cause this, they would reboot or give blue screen...

But a CPU issue would in addition to causing a system freeze allow the monitor to go in stand by mode, once I left it frozen overnight and the monitor remained on ...