1) If the theme works inadequately, first of all, it would be wise to check whether it is installed to the correct folder. All theme files and folders must be stored here: …/wp-content/themes/dt-slash/
This theme is path-sensitive, so it will not work properly if it is installed to the wrong folder, for example: …/wp-content/themes/dt-slash/dt-slash/, …/wp-content/themes/slash/, …/wp-content/themes/slash wp/, etc.
2) Secondly, we suggest you to check whether the folders listed below have 755 CHMOD properties set: …/wp-content/, …/wp-content/themes/, …/wp-content/themes/dt-slash/
And finally, make sure …/wp-content/uploads/ (and all its children folders) has 777 CHMOD settings.
3) Some servers require 755 to be applied to …/wp-content/themes/dt-slash/resize.php file. Therefore we suggest you to check this option either. If you do not know how to deal with CHMOD settings, please, follow “How to set CHMOD properties?” instructions.
4) Please do not forget to check whether your image size does not exceed hosting file size limit. You can find it next to “Maximum upload file size:” label on WordPress uploader tab.
5) Make sure image files do not include any specific symbols. For example “+”.
6) If these steps give no result, please try deactivating all your plugins.
7) The problem also can be related to the temporary address of your web-site which includes “~” symbol. But do not worry, as soon as you get a common address, everything will work correctly.
8) Images should be stored in default …/wp-content/uploads/ folder: follow Dashboard -> Settings -> Media . Select “Organize my uploads into month- and year-based folders” for WP 3.5 and above. If your WP version is below 3.5, just leave the appropriate field (path to /uploads/ folder) empty.