migrating from single disk to RAID 5

I've moved our database from a single 30G drive with reiserfs (3.6.25 on
kernel 2.4.9) to a 4-drive RAID 5 of 80G disks with reiserfs on that
(yeilding 167G). The performance is fantastic, but the backend server
is periodically crashing.

With almost no information whatsoever, anyone care to speculate on if
this is:
1) hardware problem (seems unlikely since the drives are < 1 year old)
2) reiserfs or kernel bug
3) problem with a) shutting down postgres, b) cp -arv /olddata /newdata,
c) edit /etc/rc.d, d) start postgres
4) something else entirely

also, if it's 1), is there something better to use to check the array
than "badblocks /dev/md0"?

Not much to go on, I know, but obviously we are in big trouble if the
database is "randomly" crashing (it seems to work fine maybe 90% of the
time), and I'm worried about data corruption..

TIA

-paul