ATI its still bad at JPCSP, so maybe the problem its that, try with the latest builds here http://buildbot.orphis.net/jpcsp/, and with win7 x64 use the JPCSP x86 and remember to activate the following option in the emu options "Enable saving GE screen to Textures instead of Memory" that will give you about a 100% speedup in almost all games, that worked for me
Edit1: And tartarus almost always give some problem, so its maybe its a emu related problem
Edit1: And tartarus almost always give some problem, so its maybe its a emu related problem