I imagine it might be "ahci" vs DOS related.
No, it means exactly what it says, which is that your volume contains a path longer than MAX_PATH in length. Windows 7 does quite a lot of things - including make quite a bit of use of both symbolic and hard links - which the Ghost toolchain does deal with because they are innate capabilities of NTFS, but Ghost Walker is probably the least-maintanable part of the system.
is there a new version of ghostwalker that might address the issue?
No; our plans were, over the life of GSS 3.x to remove it entirely from the toolchain and simply fold everything it did into Ghost itself, because the code in Ghost Walker was far too poorly written to continue to maintain and we had higher-quality replacements for everything it did already inside Ghost.
However, since in early 2009 (prior to Windows 7, which GSS 3.0 was on plan to launch alongside) the ensure Ghost Solution Suite product was cancelled and the staff laid off, so that did not and will not ever happen.
Symantec's plan is (and has been since 2007) is that all Ghost Solution Customers migrate to the Altiris Deployment Solution product (which uses most of the Ghost cloning toolchain, but is entirely built around use of Sysprep) instead. You are expected to use Sysprep for Windows 7 now and into the future.
Of course, there's no value in running Ghost Walker in a lab-type environment anyway; you don't need unique SIDs in that environment, so while you should have dropped it from your process anyway there's almost certainly no value for you in using Sysprep instead.