using alt-mouse dragging to select a vertical block (column selection mode) is broken since v8 — font Tahoma, english text — the block is selected to the right of clicking point. And if you click at a long line’s tail (200th character) the offset would be … 50 characters.
v7 was ok.
I don’t see any problems. Can you try another font, fixed-width font such as Courier New? Exactly what version of v8 do you use? Please send me a screenshot that explain your issue. Thanks!