you can set maximum savings to 0 and it will hold their savings safe.
i have the fix for multiple deposits if youd like it early (its included in 1.4 final of course) but youll have to PM me an email address to send to. (copy/pasting off posts never works out)
as for loans - set them to max 1 (or 0) if you havent already. this is also included in 1.4 final, but is too extensive to send you a fix for.
the reason for this bug is actually due to a mysql limitation

which prevents me from accurately using a cron.. until 1.4 final is out the deposit fix will at least prevent losing credits.