I have had this problem for a few years, over several versions of Photoshop in several Mac operating systems. Currently I am using CS4 on a Mac 10.6.8. My space bar randomly stops typing a space when I am typing a line of text. I can type every letter except a space. Sometimes the space bar starts working properly if I save the file and start typing again. Sometimes I have to quit Photoshop to make the space bar start working properly. The problem doesn't happen often, but when it shows up it is annoying for awhile. Any thoughts as to where I might look to solve the issue?