I have been using an HDMI splitter for some time now - no name brand from the interwebs - its always been a little bit of a mission to get set-up when ever I install a new device (source or display) but once set-up it works flawlessly.

The problem is I have just had my projector returned after having its main board replaced by the manufacturer and cant seem to get the switcher going again.

I started with everything powered off, switched on the display, switched on my receiver, switched on my Apple TV (feeds through receiver) - picture displays on screen. Next I changed inputs on my receiver to my HTPC and the booted the HTPC - HTPC picture displays on screen.

Here is where it gets interesting - if I swap inputs back to the Apple TV, no display, going back to HTPC is the same, no display. 

Its like its setting everything up and handshaking but then losing it all when I change inputs. 

Anyone got any ideas on what to try next?

If I have to I can use my receiver as a splitter as it has two HDMI outs but the issue with that is it passes both displays to the input device so when I change display the HTPC has to go through the whole new monitor detection routine which results in the screen flashing a couple of times and being unusable for a minute or two. The standalone splitter just keeps the first display used in memory and uses that so the HTPC never sees a change.