...programs run normally, but the effects are very sluggish. How can I fix this?
Disable Detect Refresh Rate, and Sync To Vblank
Install drivers for your Graphics Processing Unit
Check to see if you're using your graphics card to its potential
you may need to install mesa-utils
do glxinfo | grep rendering
you should see Direct Rendering: Yes
In your cause hopefully it will say no which means that you need to install the proper drivers for your video card.
If you are using the newest Ati propriety drivers the problems could be the Tear Free Desktop setting.
Go to the Catalyst Control Center and find Tear Free under the Display Options and disable it.
This is what was causing sluggish effects on my machine, but because you didn't give us much detail on your problem, this answer is just a blind shot...