It's usually when you try and stitch an edge which hasn't got another edge to stitch too. - hope that makes sense.
So in the unwrap editor, if you select an edge and another edge in the editor turns blue, it's able to be stitched together.
However if another edge doesn't turn blue then it cannot be stitched.
You can click ok and close the window however save the scene first, close max, re-open the scene and carry on what you were doing
If you don't close max and try to edit the UV's they may go all strange when moving, scaling, rotating them.
Replies
It's usually when you try and stitch an edge which hasn't got another edge to stitch too. - hope that makes sense.
So in the unwrap editor, if you select an edge and another edge in the editor turns blue, it's able to be stitched together.
However if another edge doesn't turn blue then it cannot be stitched.
You can click ok and close the window however save the scene first, close max, re-open the scene and carry on what you were doing
If you don't close max and try to edit the UV's they may go all strange when moving, scaling, rotating them.