C#, VS2008
When having a vertical (block) selection in the clipboard buffer and switching between the two last inserts with Shift+Ctrl+V, the buffer looses its "vertical/block" information and becomes a normal insert.
e.g.:
singleLineInsert = false;
this.var1 = 0;
this.var2 = 1;
this.var3 = 2;
this.var4 = 3;
Select first line, Ctrl+C it, select parts marked in red, Ctrl+C them, Ctrl+V, Shift+Ctrl+V twice.
As you should see now, the first time the block is inserted correctly, the second time its inserted as 4 separate lines.