If you pose a figure (especially if you apply a full pose to the entire figure somewhere along the timeline) then every body part which is different from the original pose will gradually morph from the first position to the next.  If using a character, be sure the character is fully open in the sequencer (use the navigation on the left to open it if not) so you can see all individual parts which move.  If you want something (hip, right shoulder, etc) not to move to the second pose, scrub to the second position (you will see this clearly as there will be several to many keyframe marks at that point in the timeline) and simply delete the second keyframe for the part.  This eliminates the change at that point in time.  If it moves further along the timeline, be aware that you will still see the morphing - it is now going from the original position to the later - over a longer period of time.  If you want the part frozen to the second movement, copy the first position (keyframe for that part at the beginning of the timeline) by using alt + left mouse button to grab the key (it will turn yellow when you grab it with the mouse) then slide the copy to the second position.  You have now indicated that the position should be the same at both times, meaning it will stay motionless up to the second instance of the key frame.  Play around, and you'll catch on quickly.

Klebnor

Lotus 123 ~ S-Render ~ OS/2 WARP ~ IBM 8088 / 4.77 Mhz ~ Hercules Ultima graphics, Hitachi 10 MB HDD, 64K RAM, 12 in diagonal CRT Monitor (16 colors / 60 Hz refresh rate), 240 Watt PS, Dual 1.44 MB Floppies, 2 button mouse input device.  Beige horizontal case.  I don't display my unit.