The method Rui discribed is the best for elements that "float" on transparency, like type, for instance. I find that it's even better if after applying it, you go to Edit > Fade, and fade the effect to about 70 per cent. By mixing the processed image with the previous state, you get to apply the filter in an even more subtle way than the filter's minimum intensity.
BUT... There's a free Photoshop action made by Adobe called "Deflickerator" (Just in case, actions are nothing more than a group of Photoshop commands grouped together as a single command that you can trigger. These actions can be shared and loaded in Photoshop's Actions palette).
It applies a sophisticated, adaptive approach to deflickering graphics. Adaptive means that it detects areas of the image where flicker might ocurr, and only "heals" those areas selectively. So you keep most of the resolution AND get rid of the flicker! The only drawback is that it doesn't work for elements like type or strokes, where flicker appears on the edges (because actually the flickering element in that case is the layer's edge and not its' content).
If you can't find it, let me know and I'll e-mail it to you. At the very least it's fun to watch it while it does its' thing
Adolfo Rozenfeld
Buenos Aires - Argentina
www.adolforozenfeld.com