Pull the fixture slightly out of the ceiling (or underside of cabinet) so that you can get your fingers around the white part of the fixture. Now, with your other hand, twist the glass lens in a counter-clockwise direction. I'm thinking that your fixture is spinning in the hole.
There are two types of recessed cans. One type has spring clips on it and is easy to get out. The other has semi-rigid metal clips that when put in are very difficult to get out without breaking a clip. Since you only need to remove the glass to replace the bulb, try not to remove the fixture itself.
By the way, if replacing with another halogen bi-pin bulb, do not touch it with your skin. The oil on your fingers will diminish the lifetime of the bulb. That, the heat and the current draw was the main reason for going to LED's.