20D Flash or Shutter Problem
It works for me.
I suggest that you put your camera in manual mode and leave the flash in ETTL.
Set an aperture for the DOF you want and a shutter speed between 1/60-1/250th depending on the situation. Set +2/3 flash exposure compensation. I like shooting at 400 ISO with my indoor flash shots. I also have custom function 14 set to 1 for average. Keep an eye on the histogram to get a good guage of the exposure. Shoot Av for fill outdoors. I also like using a diffuser like a Sto-fen Omnibounce or bouncing off the ceiling. I like using a Lightsphere II, but it is a bulky piece of equipment.
Canon FiveDee, Canon 2oD, Canon Gee3, and Canon S7o, Fuji Eff30.