It is a known bug of Zsnes with the card and its drivers, with both ntsc and hq filters. You will get better support for Zsnes if you visit the official site forum, since this site is mainly for emulators of newer systems. By the time being you can either simply use another filter than those two (2Sai is the best general filter in my opinion in any emulator that i used), another emulator like Snes9x, or wait for a new version/ driver for your graphic card that fixes the bug.
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System Specifications: Athlon64 3200+ @ 2,12 ghz, 1GB DDR RAM, 9600GT 512MB, 200+250 GB HD, Windows xp sp3