I Did a quick forum search about this and didn't find this particular issue dealt with, so here goes (please pardon me if this should be posted elsewhere -- it didn't seem to fit any of the main categories):
When using KWin's zoom desktop, I found an interesting little glitch. When restoring to normal view from a zoomed view the mouse pointer disappears. The problem can be worked around by unchecking "Suspend desktop effects for fullscreen windows" in the advanced section of Desktop Effects.
The issue appears to be hardware independent (unless it's related to AMD processors) I've noticed it on 2 different machines that use different video cards, memory types, processors (one is a 32 bit AMD XP Athlon the other is a 64 bit core AMD Turion) and mainboards. I don't remember seeing this issue prior to KDE 4.8.x
I would be interested if anyone else has seen this.
To reproduce the glitch:
1) Zoom feature must be enabled in Desktop Effects
2) "Suspend desktop effects for fullscreen windows" must be checked
3) Zoom the desktop
4) Unzoom/restore the desktop
I am running fully updated KDE 2012.08 computers.