Version 6.11 is totally unsupported, so you would need to upgrade to a supported version to get any help from the REsponse center
DP 6.2x, is currently supported, but, support will go away at the end of 2014
DP 8.1 is the most current version, but there are a lot of problems with that version, and, in any event, there is no direct Upgrade path from 6.11
I checked the DP 7 installation and Licensing Guide
There is a direct upgrade path to DP 7 (Chapter 4)
So, you can either
Upgrade to 6.20, install the 6.21 patch bundle, and the succeeding patches, knowing that this will be unsupported in 6 months
or
Upgrade to DP 7, install the 7.03 patch bundle
Having said all of this, upgrading to a suppoted version is not going to fix the problem if you are trying to Restore a NDMP backup using a non-NDMP device