Blender - Vertices are splitted

Hello guys,

i’ve got a problem with my vertices… they’re just destroyed and single one now.

Someone has the same issue and a solution?

How did you uv unwrap
Are the actual faces separated in the mesh or just the UVs ?
Have you removed doubles (select all and W / Remove Doubles), then unwrap again after you have applied suitable seams etc

Thank you a lot for the fast answer. Removing the doubles worked well.