Have a Canon 40D. After using a external flash, the internal flash is not popping up. It still thinks the external flash is there. What do I do to reset this?

SOURCE: Internal flash not working because of non compatible flash installed

Solution:
Look at the external flash socket.
With the camera in "normal position", i.e., poiting away from you, you shoul see a very small (I realy mean very small) piece of plastic under the rigth inside of the flash shoe... it is the "external flash sensor". It probably is stuck. Work with the point of a knife to try and release it.
In more detail, if you look carefully at the external flash shoe, the are two metal pieces that will help create some pressure. So the flash holder (shoe) is made of two parts: a very rigid one and the metal blades that create the pressure. Look under the blade located nearest to the shuter button.
If you can locate the plastic piece (black in my camera, but can be white) try to have unstuck.
Worked with my camera.
regards
Mig

SOURCE: Canon Internal Flash will not Pops up and will not

Is it trying to pop the flash and making noise, or is there no noise at all?
If it's audibly trying and it won't pop up, it's stuck and something is blocking it. May need to send it in.
If there is no sound, then something is making it think that there's an external flash attached. Check out this photo here:
http://www.flickr.com/photos/dougpardee/133066175/
Doug Pardee on flickr may be able to help as well.

Hope this helps you! If so, leave me a rating!

SOURCE: My canon eos 40D keeps playing err-05 which says

If the camera thinks you have an external flash attached to the hot shoe it will not allow the built in flashto pop up. so you can try this...
Here's a very simple solution I found to get the flash to pop up without destroying your camera.
http://forums.dpreview.com/forums/read.asp?forum=1031&message=31993875
the person suggests using a fingernail. (s)he must have long fingernails. I had to use a piece of paper folded in half. Swipe the paper from back to front, as in, from the eyepiece side towards the lens side.
Here's a picture: http://www.flickr.com/photos/dougpardee/133066175/
good luck