mariking seams in 2.69 causes UV layout to come undone

The title says it all. I’m working on a mesh in 2.69 official release, but when I try to add a seam or change a seam’s layout in a blender file, in either the 3d window or the UV window, the mesh blows up and immediately drops all UV orientations. So that the unwrapping work is destroyed.

Again, no matter whether I do it in the UV window or the 3d Window the result is the same - the UV layout comes apart. Why?
And is there is fix to enable marking seams in the 3d window. I seem to recall I could do this in earlier versions without the UV layout collapsing. I also removed any mesh modifiers but no joy. Still same outcome.

MY workaround … I export the mesh out to OBJ format. Then I can do work on adjusting or adding/deleting seams without destroying the UV layout. When finalized, I import the mesh back into the blender file. But … this doesn’t seem to be how things should work.

PS: I also noted that when I saved the streamlined obj file as a blend file I could work also mark in new seams and make adjustments without the mesh destroying itself.