Consider a document with two lines. Line 1 is longer than line 2. Switch to block selection mode (ctrl-shift B) Go to the end of line 1. Press the down arrow. Since in bloc edition mode, the cursor is now located after the end of line 2. Now press Ctrl-left_arrow. Kate (or kwrite) hangs. Using kate 3.8.1 (kde 4.8.1) compiled from gentoo packages.
fixed in 4.8.2. *** This bug has been marked as a duplicate of bug 286887 ***