It seems that the console completely locks up when attempting to start a game whilst the GameShark is attached to the unit. Oddly however, I am able to use the V-MEM functions just fine. It will load the virtual memory card and reboot the system. I was just curious if anyone else had ever ran in to this issue. Thinking about flashing the GameShark with an AR rom and seeing what happens.
Does it have a switch on the side? Try booting the PSX. selecting your cheats and then flick the switch down to turn off the GS, once the game has loaded, turn it back on. Also try cleaning the contacts on both GS and PSX.
The GS Pro's have a push button not a slide switch so there is no real way to enable/disable like the older ones.
Just an update. I managed to restore it with XFlash and it's working great now. Thanks for the suggestions!