[arch-general] strange behaviour after 3.18.6 kernel update

I have one server which does internal mail and nfs - which went weird after about a day on the new kernel. I remote admin via ssh - symptom on the terminal was many commands failed in bad ways. Though 'ls' seemed to be fine. e.g. vi - gave input/output error. journalctl -lf -> bus error Rebooted and it hung on shutdown - there were manu input/output errors on the console - after it stopped on systemd shutdown target and got no further - i hard powered off and back on. Machine came up fine - journalct shows all logging stopped at 9.14 pm and resumed as normal after the reboot at 10.30 pm. Any advice as to what to look for? Anyone else seeing strange IO errors after a period? thanks. gene