Why do I get a system error on Series 60? It worked fine before.
A system error is usually triggered if an application UID is not correct or a resource file is incompatible with the application executable file. If the application was working fine before, it means that one of the resource files (the package file, project file or resource file) contains a different UID than the application itself. Check to see if the UID is the same in each project file.
It can sometimes happen that a resource file (with the extension .RSC) isn't updated correctly. Check it's date to see if it was built around the same date as the application file (with the extension .APP). If the resource file is outdated, delete the temporary build and data folders for this project. The temporary build folder can be located at \Epoc32\BUILD and the data folder can be found at \Epoc32\Data\z.