Since you are having issues with the IR functionality while the TV is on, we will need more information about your layout.
Are you using the Slingbox as a pass through? (A/V source -> Slingbox -> TV)
Is your TV connected to the AV source with an HDMI cable?
We recommend you to be as specific as possible about the issue you are having. This way, other forum users will be able to help you with accurate information.