Fixing permissions as far as I know fixes problems often associated with Force Close errors. When files updated or written by the Android OS they are often written so you can for example read only. The files are changed to 755 access which allows you to read, execute, and write to the file. This can clear any problems programs have when accessing files. This is how I am perceiving it and may not be correct. Its what I know from my unix/linux noob days. Someone with more knowledge can come enlighten us.