horizontal scrolling not working

1) «Just lost the "shift + mouse wheel = horizontal scrolling" function.»

Doesn't work for me either (using Mac OS X 10.5.8 Leopard, X11/Xquartz 2.4.0): not with Inkscape nor other GTK+ applications like GIMP. I have not found a setting (neither for OS X nor for X11) to make it work, and the same problem has been reported for Inkscape 0.46 and 0.47 on OS X 10.4.11 Tiger.

known alternatives:
a) mouse-dragging the scrollbar ;-)
b) tilting the mouse scroll-wheel to the left/right (if available)
c) <scroll-wheel> while hovering over the horizontal scrollbar with the mouse
d) gestures (2-finger wipe) on the trackpad (if working on a laptop).

2) «couldn't cut and paste one particular image without crashing inkscape.»

The crash is usually caused by one of or a combination of
  Bug #211607 “Crash when pasting raster image due to unwritable directory”
and
  Bug #307005 “[OS X] copy & paste inserts a bitmap copy instead of the vector object”

workaround in Inkscape 0.47 on Mac OS X (Snow) Leopard:
a) Copy&paste of vector objects: change the X11 preferences for the pasteboard as seen in this screenshot:
<http://launchpadlibrarian.net/36209214/XQuartz-clipboard-preferences.png> or described in the FAQ <http://wiki.inkscape.org/wiki/index.php/FAQ#Copying_and_pasting_in_Inkscape_creates_pixellated_images_instead_of_copying_the_vector_objects>
b) Pasting of bitmap images from the clipboard into a new Inkscape document: save the Inkscape document prior to pasting from the clipboard to avoid a crash as described in bug #211607 (comment #35)

Note: since you applied the magic woodoo (SCNR) of 'repairing permissions' it is possible that you now do not have 'write'-permissions for some of the folders Inkscape wants to use to store the PNG file containing the pasted image. Try changing the X11 pasteboard settings first, if this does not help, report back and we will try to figure out if there are other workarounds to stop Inkscape from crashing.

Follow-up on the horizontal mouse scrolling issue:

I was wrong in assuming just because it doesn't work in GIMP's document window either that it fails in GTK+ applications running under X11 on OS X in general: this is not true. It turns out that even other widgets inside Inkscape itself know about <Shift>+mouse wheel and scroll horizontally as expected (examples are the palette window just below the canvas, or the pane on the right side in the preferences dialog.

-> Possibly some (internally hard-coded) filtering for keyboard shortcuts grabs the 'Shift' event for the main window and in effect prevents that X11 and/or the system receive the key press state when using the mouse wheel to scroll the canvas horizontally.

I have re-opened bug #167191 “no horizontal scroll on OS X”:
<https://bugs.launchpad.net/inkscape/+bug/167191>

Same here, not Shift + Scroll vertical srcrolling on Ubuntu 16.04 with Inkscape 0.91 r13725.

http://stackoverflow.com/q/1175192/632242 solved the problem for Firefox, but still not working with Inkscape...

Any idea?