More often than not, on booting to Kubuntu 12.04.01, I get a pop-up message "An application has crashed, now or in the past". I dismiss the message and everything seems fine. Occasionally when booting recently to Windows XP as administrator (though not as regular user) I have had an equally non-informative message "Your system has recovered from a serious error".
Should I be worried; if so, how do I find out which application and fix the problem?