There were a bunch of 7200.11 models that had firmware issues causing the drive to slow down and eventually stop working. The data is still there but it just won't spin. Happened to my 7200.11 i bought back in 2008. Drive started slowing down and within a month stopped working in 2010. I googled my model by serial and found a bunch of threads where it was happening to a lot of people. The fix was a firmware update but I couldn't apply it cause my drive completely stopped working.
I would contact seagate with your serial number and see what they can do for you.
Cheers mate ill call tomorrow