Cannot add internal links to documents in IE8

In IE8 it is impossible to add internal links to documents, assets or images.

Steps to reproduce:
1 Open document for editing
2 Type some text and select it
3 Click "Add internal link" button
4 Select an asset, document or image via dialog
5 After returning to document click "Save"
Expected: internal link is saved
Actual: text typed in 2 is deleted and no internal link is created.