...
EDIT #1: You don't need to answer these questions, I probably know the reason: The information-querying timers are disposed after killing the daemon (and wallet) process, thus, causing a crash when they are executed after the processes have been closed.
EDIT #2: Also, when I switched to using the RPC version of simplewallet, I didn't realize that it does not support the 'exit' command (for safe shutdown), so the next release will contain a fix for this, too.
~CfA~
Right, I wouldn't be asking for donations if it did so.
You can check the source code, and even compile it for yourself if you wanted to be extra careful.