All I did was to record the macro while rotating the picture and then clean up the code. I tried to import a new picture and rotate this with the same code, this also worked.
I'll send you the spreadsheet if you mail me at mgp@mxl.dk
I know that some objects cannot be rotated (e.g. a text box) and I have also wondered sometimes objects are no longer rotatable even though I recalled they used to be. Never found out why though.
Could it be the properties of the picture that causes the rotation angle to freeze/lock?