Fanjita has brought up the issue that some people are having problems with the 0.7 build of LUA, and has brought a recent patch to our attention:

A lot of people have been having trouble with the 0.7 LUA build. It's something to do with the PSP messing with hidden filenames, under conditions that don't completely make sense.

Anyway, there's now a patch that should fix it.  This is a tool to improve the stability of the bundled USER_LUA player for EBOOT loader 0.7. Replace your USER_LUA folder with the contents of this archive, if you're having problems with the 'error [string "?"]:61: unexpected symbol' error on v0.7.

You can get it in our PSP Download section [here]