I have two kSpam v1.5 installations, and both are affected by this problem. I think it is most serious bug with current versions, because causes unexpected server crashes - and this is not acceptable in production environments where several-month-uptime is expected.
In most cases server crashes, when bload updates probability files.
Only (partial) workaround I know, is to run bload only once a day - this changes mean-time-between-crashes from days to weeks. I'm using two program documents in domino directory:
10:00 AM - program: bload
10:30 AM - program: nserver, commandline: -c "tell bload quit"
By the way, 'nice to have' is option to bload (eg. bload once) to enforce task shutdown after recalc