Spamassassin runs for a long time (10 minutes or so) and takes all CPU time until server hangs.

I use Debian Sarge and Postfix for MTA. Could this mean that my server is used as I spam relay, how can I be sure?

I would rather disable Spamassassin then have server crash every day.

Please, please give me some tips on where to look for problem.

Thanks

Here's how it looks like from top:

top - 00:10:19 up 9:06, 2 users, load average: 2.22, 1.42, 0.69
Tasks: 106 total, 4 running, 100 sleeping, 0 stopped, 2 zombie
Cpu(s): 26.8% user, 73.2% system, 0.0% nice, 0.0% idle
Mem: 905400k total, 848220k used, 57180k free, 57260k buffers
Swap: 5863640k total, 128k used, 5863512k free, 471808k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
32563 anda 20 0 25240 24m 2544 R 49.7 2.8 2:02.88 spamassassin
32574 liga 14 0 25240 24m 2544 R 49.7 2.8 2:02.52 spamassassin
25629 root 11 0 1092 1092 848 R 0.7 0.1 0:17.42 top
1 root 8 0 500 500 448 S 0.0 0.1 0:02.09 init
2 root 8 0 0 0 0 S 0.0 0.0 0:00.00 keventd
3 root 19 19 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd_CPU0
4 root 9 0 0 0 0 S 0.0 0.0 0:00.01 kswapd
5 root 9 0 0 0 0 S 0.0 0.0 0:00.00 bdflush
6 root 9 0 0 0 0 S 0.0 0.0 0:00.00 kupdated
18 root -1 -20 0 0 0 S 0.0 0.0 0:00.00 mdrecoveryd
75 root -1 -20 0 0 0 S 0.0 0.0 0:00.00 raid1d
103 root 9 0 0 0 0 S 0.0 0.0 0:03.37 kjournald
235 root 9 0 0 0 0 S 0.0 0.0 0:00.00 kcopyd
564 root 9 0 0 0 0 S 0.0 0.0 0:00.00 khubd
1347 daemon 9 0 452 452 384 S 0.0 0.0 0:00.12 portmap