Onxy is a well respected freeware third party utility:
http://www.titanium.free.fr/pgs/english/apps.htmlBoth it and SmartReporter are safe. I have been using both for years.
/private/var/log/windowserver_last.log is invisible. You have to use a utility to turn it visible to find it. I recommend Invisibles 1.5:http://www.versiontracker.com/dyn/moreinfo/mac/14722Download it and put it into your Utilities folder. Then open it and click the radio button to turn invisible files and folders visible. (Your finder will disappear for a few seconds, then re-appear with invisible flles and folders visible.)
Then go to
/private/var/log/ and check the size of windowserver_last.log. Mine is 100K. If it is much bigger than that, delete it. Also check the rest of your log files. My biggest log file is 1.5megs and all the rest are under 1 meg.
Once that is done re-launch Invisibles and click on the other radio button to restore the default visibility to your files (again, Finder will disappear for a few seconds).