Unfortunately, it detects protective settings applied by Spyware Blaster and similar tools, as being the malware these tools are protecting against. This is a generic type of bug that often arises when tools assume anything other than default is a hostile change, or when overly-loose detection cues are in effect.
Specifically, settings within HKCU's P3P\History that block unwanted cookies, are detected as evidence of malware. In the case I'm currently working on, only around 5 of over 100 protective entries were detected in this way.
The tool then claims it is unable to fix these problems, which is just as well, as doing so would actually weaken system safety. The end result is similar to Winfixer et al, i.e. false-positive (actually, reverse-positive) detections plus referral to feeware products if these are to be "fixed" - so one hopes Symantec will fix this sooner rather than later.
The case I'm working on is interesting, as it was brought in because it was slowing down, with malware as the suspected cause. Formal scanning finds no active malware, and one wonders if the slowdown was the result of installing Google desktop etc., with the false-positive from Norton Security Scan as the red herring.
I'd like to try Norton Security Scan within mOS contexts such as Bart or WinPE CDR boot, but it appears as if the product is available only via Google Pack. There are no references to it at Symantec's site, and the FAQ doesn't seem to consider "so where can I download this thing?" to be "frequently asked".