osx is 10.8.3I haveCan you tell us a few things about your Mac?
Which Mac do you have?
What version of OS X are you running?
How much RAM memory is installed?
and finally - How much free space do you have on your hard drive? (That would also be space available on your hard drive)
I _don't_ think the Activity Monitor shows crash reports. Usually, all you see is a process that might show "Stopped Responding", or the CPU may show high CPU use for a particular process. Be sure that the process drop down in Activity Monitor shows All Processes, and not just My Processes.
You should also be able to determine which process is showing problems.
What's the name of that process?
You can also go into your Console (in your Applications, then the Utilities folder, and open the Console), and look through the system.log - which will be listed by time and date. That log can be quite large, and scrolling down to the approximate date and time can help you look for other system messages that you recorded in the log. You can copy and paste a few relevant lines here. 20 or 30 lines should be sufficient.