Ok, tried Lock'n'Chase, same reset, with guru meditation error as the previous games (#81000009. 00C09E3C). So, is it the 512k ram expansion? Changing the subject: do you accept game requests? Since you evidently have above-average programming skills, you should consider making an Amiga port (possibly ECS/OCS) of Tehkan World Cup, and making it trackball compatible. It's always been my arcade obsession (and not only mine, I think).