Once you post your computer Make & Model of your hardware and GPU card/ Integrated Graphics, Motherboard, Processor, HDMI Switch, and how it is exactly connected from the GPU/Motherboard to the HDMI Switch and from the HDMI Switch to the TV and PS3. I might be able to suggest some troubleshooting tips.
Can't you use two HDMI Cables from the GPU Card(?) to the TV and PS3?
If your GPU card or Motherboard only has one HDMI Output, you can purchase a DP-HDMI "active" adapter to connect your TV or your PS3 and get rid of the HDMI Switch.