A plugin to easily present source code on your site with syntax highlighting and formatting (as seen in code editors, IDEs).
If you are using the WYSIWYG (rich text) editor to compose your post then that is what's messing things up for you. iG:Syntax Hiliter does not support composing posts and posting code using WYSIWYG at present. If you are not using WYSIWYG editor and still have same issue, please report it.
By all means, feel free to submit a pull request.
Please feel free to suggest a new feature. Its inclusion might be speedier if you can provide the code to make it work.