Norton Antivirus for Mac (NAV)--the consumer product--is Snow Leopard compatible as of version 11.0.3.
Symantec Antivirus for Mac (SAV)--the enterprise product--will be updated to 10.3 in November or December (likely December) for Snow Leopard compatibility.
If you have entitilement to SAV (either through SAV for Mac or SEP Multi Tier) but need protection now on your Snow Leopard machine, you need to open a case with Support to obtain the workaround (as mentioned in the "Compatibility with Symantec AntiVirus for Macintosh 10.x and Mac OS X 10.6 Snow Leopard" document above).
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