Try a reset of IE.
Start menu/Control Panel/Internet Options
Reset Internet Explorer settings is at the bottom of Advanced.
You will asked to confirm that you want to Reset. At this point, you can either delete personal settings or keep them.
When you reset Internet Explorer you can uncheck Preserve Favorites and you will not lose any sites in Favorites.
Preserving Favorites has nothing to do with bookmarked pages. In this case it refers to things such as your home page (which will be changed to MSN if you have a different homepage), saved sign in names and passwords, default search provider (will be changed to Bing) and other things related to how you have IE set up. You can easily change the homepage and default search provider to those you prefer.
If IE is open, you will have to close it before it will reset.
After you reset IE, see if you are able to post on Facebook with Internet Explorer.