Hmm so it looks like the error is not coming from SilverStripe layer, since you are in dev mode and have emails enabled.
I think my next step in this case would be to hijack the query function call (probably in MySqlDatabase.php) and add some logging mechanism to dump all the executed queries (firebug, var_dump, or write to a file). Then you can have a look through raw queries and find the last one before the server crashes (probably the UPDATE one that stores the "select from" thing, right?).
Then you could try this query in phpMyAdmin directly to see if it's something with the query itself.
I'm running SS 2.4.3 and I'm having a similar issue anytime the word select or from is in the content I am trying to save it causes an Error Saving Content message and an 500 Internal Server Error tried the patch mentioned in this thread but that does not solve the problem.