Can't create savedata for THUG2 Remix on PSP

Hi all,

When I boot up Tony Hawk Underground 2 Remix for PSP via Adrenaline, it tells me that there's not enough memory free on the memory stick duo to create a save. I have a 512gb SD card via sd2vita, and about 398 gigs currently free. All of my other PSP and PS1 games have no issues creating saves, and they show up under the saved data icon on XMB.

Anyone know why this is happening and how to fix? The only thing I can think of is that all of my other games are directly from pkgj, whereas for Tony Hawk, I downloaded the iso and put it on the sdcard myself. The filename is just the name of the game, rather than UCUSXXXXX or whatever it would be. Do you think this is what's causing it?