grab application seems to be broken?

hello... my grab screen application has been working fine since i first got my mbp, using both cmd shift3 and cmd shift4, also with ctrl included. now when i try to do either an image is created, but the image is only a cream image with black diagonal lines across it, and that is obviously not what i intended it to look like. i have tried to view the settings for the application, and i have not changed a thing as far as i know. i hope someone can help me with this, as its not particularly important, but rather annoying.

thankyou