Problem
After installing SL4A_r4 (Scripting Layer for Android), on your Android phone, and before installing any interpreters every time you start your SL4A app, it keeps crashing after a few seconds.

Solution
If you install an interpreter (ie JRuby), then the application stops crashing.
You would need to be quick to start the installation before the application crashes, by doing the following:

Settings -> View -> Interpreters -> Settings -> Add and then select the interpreter you would like.