Hacking pops memory card problem - can 1 card be hidden?

[mechagouki]

So I'm on a bit of a PSX first person shooter revival at the moment. last night I converted an old favourite of mine; Lifeforce Tenka. I've done plenty PSX2PSP conversions so I know I did nothing wrong there, the game loads fine, the opening CG movie plays etc. but when I try to start a game a message pops up that says "Please remove one of the memory cards" and will not allow me to progress.

Is there a way to make pops only load one virtual memory card? I've never seen this issue in another game.