[exim] spamassassin problems

I runs exim 4.63 with the last spamassassin.

This is runnig around two months with tis configuration.

And now i have a lot problems whith load average,
my cpu is

model name      : Intel(R) Pentium(R) 4 CPU 3.00GHz
cpu MHz         : 3000.611
cache size      : 2048 KB

and my kernel 2.6.8-3-686-smp
and i have 2 G of memory

and i have a lot of somby process

 1828 spamd     25   0  193m 187m 4780 R 99.9  9.3   8:23.69 spamd
 1830 spamd     25   0  186m 181m 4780 R 99.8  8.9   7:17.11 spamd