Audiophile 2496 S/P DIF Issues

Hi guys, not sure if anyone can help me on this, but there might be something simple I need to check before thinking of redoing my whole system...

I installed a new Audiophile 2496 card into my PC yesterday (HP running XP Media Centre Edition with onboard audio disabled in BIOS) and everything seemed to be fine. I had done a clean install of XP, and after I installed the card I installed Sonar (Producer 5), everything was still fine. I was recording audio from my Korg workstation and into the S/P DIF input of the card with no problems at all. Later in the day I noticed that I no longer had any audio coming in from the S/P DIF input. After scratching my head for quite a while I started playing with hardware settings in the 2496's control panel. I discovered that when I set the 2496's master clock to 'S/P DIF In' then it recognised a signal from my Korg, yet I had left the master clock set to 'internal' earlier on and still had S/P DIF signal. So in other words, I cannot get an S/P DIF signal when the master clock of the 2496 is set to internal... and I'm not sure why! It tells me that the signal is either invalid or not present.

I'm really lost on this one, is there anything obvious that I should be checking? I've uninstalled the driver for the 2496 and reinstalled it, uninstalled Sonar (in case it had anything to do with it), and checked all possible settings on my Korg (Triton Studio), tried the card on both ASIO and WDM drivers from within Sonar... hasn't helped.

Ok, thanks for that. Makes me wonder how on earth I was receiving S/P DIF signal while the master clock was set to internal. My Korg only outputs as low as 48k, which totally mucks up any playback of 44.1 sources from the pc, so I'm positive the master clock of the 2496 was set to internal previously while I was still getting a valid signal. Anyhow, I can at least know that something major isn't wrong, thanks again! :)