Relates to: T31951
As you can see in the attached picture, when the loop its slide or if a loop cut its done using the "Correct uvs" option, the vertex at the uv editor will be splitted, they move just a bit but its enough to generate some issues, with the selection and the subsurf modifier.
1- create a mesh
2- do a uv map , any one will work
(a grid and a unwrap its the simpliest)
3-select a loop at edit mesh
4- Use "Slide edge"
5- at the operator menu activate "correct uvs" ( at tool shelf or F6)
5B- create a new loop using "loop cut and slide" (Ctrl+R) if you ar using this remember to activate the option "correct uvs" under the "input" menu at the "User Preference" . Its Disable by default and the operator dosnt have redo so it needs to be active before cut.
6-check the uvs at the uv/image editor
you should find that the vertex slided and the neighbours were splited.
blender 2.63a official
and build from graphicall rev 46913
but this remain the same since 2.62 i cant remember exactly witch revision, probably after bmesh
Another thing I found this report, http://projects.blender.org/tracker/index.php?func=detail&aid=29771&group_id=9&atid=498 its near but its not the same thing