Whilst in Vehicle or Space Plane building mode I am unable to pick up any of the Mech Jeb parts once I have placed them. As a result I have to restart the entire build if I misplace anything. AR202 works fine, It's the pod parts that don't work.

I also have a similar issue, but it extends to all mechjeb parts. Once placed they cannot be moved, nor can items be attached to them, nor can they be selected or manipulated in any way. Further, none of the mechjeb parts in the pod category can be placed first. Running KSP 0.20.2.186 on windows with MechJeb 1.9.8

I, too, experience the same problem; I can't pick up the 2.0 pod, the 1m edition, the radial edition, the fuel tank, the engine, and the decoupler, to be precise. Everything other MechJeb part works fine, though I still can't select any of the mech pod parts as first part either.

Items can be attached and detached to the immovable parts, and they can be moved with its parent part, if they were placed on a movable part; as soon as they're placed, though, be it floating in the air or attached to your vehicle, not even Ctrl+Z can get rid of them.

I'm running the same version as above.