Norton Internet Security 2009 just recently updated from version 18.104.22.168 (which generally worked fine) to 22.214.171.124.
The new version isn't exactly working too hot with some installations of Windows 7, particularly the 7057 build.
You can try to uninstall and reinstall the older 126.96.36.199 build of NIS, but within 48 hours or so they're likely to start pushing the new update in and cause problems again.
Similar issues are occuring with Norton 360 v3.
They are aware of it: Win 7057 updated to NIS 2009 188.8.131.52 now black screen - Windows 7 Beta Compatibility - Norton Community
Anyway, the only fix for now seems to be uninstalling (in safe mode) and likely running the Norton Removal Tool, and finding something else or doing without.