Keyboard stays on when viewing images sent in text messages iPhone 4

Sometimes when I am receiving images in text messages, tapping on the image wont remove the keyboard. It stays there, covering the bottom part of the image. When tapping the senders name (to go back to the previous screen), the keyboard stays on and continues to do so when going back one more time (to the messages list). When exiting the Messaging app and coming back to it, the keyboard is gone, however, the input field with the camera icon and send button stays in the center of the screen.
The only way to get rid of this after it has happened is to close the messaging app via the multitask menu, so I can live with that.
Does anyone have the same problem? It seems to have started after the OS 4.2.1 update
MacBook Pro Core Duo 2.16 Mac OS X (10.6.5)