This happens when the cache gets full and doesn't realize it, as goojamin said. I was convinced we had solved these issues...
Don't you have similar issues in 0.15.1? The current SVN should actually have huge performance improvements...
- if your psp is a 2000/3000/Go, make sure you have the 64MB memory mode enabled (in other words: make sure you have a Hen or a CFW). If you have a psp 1000, you're out of luck on this one
- make sure you're not using high resolution images for cards
- use tiny crops instead of "normal" psp images. This divides memory usage by 2. see: http://wololo.net/forum/viewtopic.php?f=15&t=2197
- Make sure the lands in your deck are as homogeneous as possible (the less pictures in your deck, the better)
- In the options, disable card images (I know, not the best, but...)