This bug has been reported to Ubuntu Launchpad as: 
https://launchpad.net/bugs/537190

From the launchpad report:

$ lsb_release -rd
Description: Ubuntu lucid (development branch)
Release: 10.04

$ apt-cache policy gnumeric
gnumeric:
  Installed: 1.10.0-1ubuntu1
  Candidate: 1.10.0-1ubuntu1
  Version table:
 *** 1.10.0-1ubuntu1 0
        500 http://us.archive.ubuntu.com lucid/universe Packages
        100 /var/lib/dpkg/status

I was using gnumeric and didn't expect it to crash.

ProblemType: Crash
Architecture: i386
CrashCounter: 1
Date: Thu Mar 11 00:46:23 2010
DistroRelease: Ubuntu 10.04
ExecutablePath: /usr/bin/gnumeric
Package: gnumeric 1.10.0-1ubuntu1
ProcCmdline: gnumeric
ProcEnviron:
 SHELL=/bin/bash
 LANG=en_US.utf8
ProcVersionSignature: Ubuntu 2.6.32-15.22-generic
SegvAnalysis:
 Segfault happened at: 0x488a7a: fldl 0x18(%ecx)
 PC (0x00488a7a) ok
 source "0x18(%ecx)" (0x00000018) not located in a known VMA region (needed readable region)!
SegvReason: reading NULL VMA
Signal: 11
SourcePackage: gnumeric
StacktraceTop:
 ?? () from /usr/lib/libspreadsheet-1.10.0.so
 ?? () from /usr/lib/libspreadsheet-1.10.0.so
 _gtk_marshal_BOOLEAN__BOXED (closure=0x8128410,
 g_type_class_meta_marshal (closure=0x8128410,
 IA__g_closure_invoke (closure=0x8128410,
Title: gnumeric crashed with SIGSEGV in _gtk_marshal_BOOLEAN__BOXED()
Uname: Linux 2.6.32-15-generic i686
UserGroups: adm admin audio cdrom dialout dip floppy fuse lpadmin plugdev video
 CancelOk


Stacktrace available:
http://launchpadlibrarian.net/42471662/Stacktrace.txt

Comments from gnumeric developer:

According to the stack trace of comment #5(above stacktrace), gtk_icon_view_get_dest_item_at_pos was called with a valid GtkIconVIew two valid integers for drag_x and drag_y and two arguments that are NULL (as permitted by the documentation). The crash happens 24 layers deeper in gtk.

I think this bug should be considered a gtk bug.