problem with segmentation fault error

Hello,
I've got problem with PostgreSQL crash (today it was twice).

Usually, average load5 is about 16-20. Today I've run new application and load has increased dramatically.

First time before crash load was fast rising from 30 to 70 (log below)
2010-01-27 10:34:01 CET [3931]: [9-1] host=,user=,db= LOG: server process (PID 24454) was terminated by signal 11: Segmentation fault
2010-01-27 10:34:01 CET [3931]: [10-1] host=,user=,db= LOG: terminating any other active server processes
2010-01-27 10:34:01 CET [21906]: [1-1] host=X.X.X.X,user=pgmed,db=pgmed WARNING: terminating connection because of crash of another server process
2010-01-27 10:34:01 CET [21906]: [2-1] host=X.X.X.X,user=pgmed,db=pgmed DETAIL: The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.

Second time, load was about 70-80 and processor utilization was almost 100% from 1 hour (log below)
2010-01-27 18:46:06 CET [3931]: [16-1] host=,user=,db= LOG: server process (PID 28357) was terminated by signal 11: Segmentation fault
2010-01-27 18:46:06 CET [3931]: [17-1] host=,user=,db= LOG: terminating any other active server processes
2010-01-27 18:46:06 CET [26377]: [3-1] host=X.X.X.X,user=pgmed_app,db=pgmed WARNING: terminating connection because of crash of another server process
2010-01-27 18:46:06 CET [26377]: [4-1] host=X.X.X.X,user=pgmed_app,db=pgmed DETAIL: The postmaster has commanded this server process to roll back the current transaction and exit, because another server process exited abnormally and possibly corrupted shared memory.

I have 8.4.0 version.

Do you have any idea where problem could be? Is it hardware or rather PostgreSQL configuration problem?
I'll be grateful for any help.

Best regards
PG