Lost CROP function

I've been using version 5.5 for a while now, and lately when i want to crop from a selection on the image (jpg, gif, anything) i go to IMAGE on the tool bar and CROP is greyed out. I can't use it. I'm in RGB Color mode as usual. If I SELECT ALL, the CROP function works, but that's useless. To get around it i'll copy the selection then paste it into a new file then flatten it, but that's time consuming. What happened?

I had this once before on a windows 98 machine running 5.5, what you need to do is quit photoshop, toss your photoshop "prefs" file and launch photoshop again.

That fixed it on the machine I found this on. Search your machine using the "find files and folders" function, for the word "prefs" and delete the file named -photoshop (blah blah blah) prefs-
Photoshop will create a new file apon restart

Your suggestion worked. Thanks buddy. P.S. My machine uses Microsoft ME. No problemo.