The forum operates in read-only mode.
Please head to StackOverflow for support.
It will be difficult to say anything about this issue if we do not know the CKEditor and IE version that you are using. Since we cannot see any such problem on our demo, we have to assume this is something specific for your installation, so you should check the error console, dev tools or whatever else for errors and differences between your customization and the standard install.
Documentation Manager, CKSource
See CKEditor 5 docs, CKEditor 4 docs, CKEditor 3 docs, CKFinder 3 docs, CKFinder 2 docs for help.
Visit the new CKEditor SDK for samples showcasing editor features to try out and download!