Flickr on WordPress.com using IE
Internet Explorer won't let you drag images from the WordPress image browser like Firefox does. Instead, you can copy the image from the browser, and then paste the image into the Post area like shown in this animation.
I used the context menu (right-click) to copy and paste in this animation.
You need to view the Original Size image to see the animation.
Note that adding an image this way does not also create a link to the Flickr page for that image like it does in Firefox. If you want to create that link, right-click on the image in the Flickr image browser and choose "Copy Shortcut". Select the photo in the editor and lick the Insert/Edit Link button on the toolbar (looks like a little chain, two buttons left of the image button), and paste the copied shortcut into the Link URL field before clicking Update. That will link your photo to the Flickr page for that photo.
Check out the Firefox animation for more info on using this feature with Firefox.