Same issue here on the same laptop: Dell's N5110. The touchpad is an ALPS and I know there have been patches posted in later kernels to address the issue (mostly for Debian likes), but on my Fedora 16:
$ uname -a
Linux ss-dell 3.2.5-3.fc16.x86_64 #1 SMP Thu Feb 9 01:24:38 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
the issue is still very present.
I recompiled the kernel with full debug support and modularized i8042, psmouse, etc to see what the initialization is up to, but that lead to a dead end. The device is picked up directly by i8042 and assigned as a PS/2 mouse without ever calling the ALPS driver (i checked the IDs, and my touchpad is indeed in the list in alps.c) If i disable the auxiliary port polling on the i8042 (options i8042 noaux=1) then the touchpad is never initialized as expected.
If anyone has any clues it will be appriciated.