safari screen fragments after short use and than locks up

Mac OS X 10.7.5, Safari screen fragments and than locks. Similar sitution with Photoshop and it's browser. The browser after a short use fragments but suddenly quits. In both cases must shut down and start up again to use the computer. Also while typing text the text response on the screen is hesitant - kind of stalls than the text will appear. Have had a Mac since 2009 and have gone through 4 OSX versions and the last update was about 2 years ago and never had these occurances. Has anyone had these same experiences and could they put me in the direction to correct this computer's behavior? Thanks