This should help
Upload and then things go blank
Blank page on upload or error message means the image is killing PHP because your using GD2 which is part of PHP. Possible things to look at.
1. Switch to Imagemagick if its on your server.
2. Lower your max image dimensions in upload options in Admin.
3. Apply the change noted in the link
4. Clear your uploads directory of all numeric user upload directories to unclog things after the changes above.
Linear Mode
