1. If you can see Extension Manager window, try to kill it and launch it again as administrator.
2. If it does not help, kill Extension Manager.
3. Rename all XManConfig.xml files of CS products to other names. Generally, XManConfig.xml is in "Configuration" folder of product installation path. For example, for InDesign CS5.5, XManConfig.xml can be found in the folder below.
5. If Extension Manager launches successfully, rename one XManConfig.xml back and launch Extension Manager again. If Extension Manager still works, rename back another XManConfig.xml and launch Extension Manager. Again and again, then you can know which product causes this issue.