Resizing columns need focusing first

Thanks for your bug report. I confirm this bug on Edgy nautilus 2.16.0-0ubuntu3.

Other applications do the same, I've forwarded the bug on GTK upstream: http://bugzilla.gnome.org/show_bug.cgi?id=386618

I've found the bug and reported the fix upstream.
Implicit pointer grab release was broken in GTK+2. It was not releasing implicit pointer grabs when modifiers like NumLock were active at the moment the button was released. The behaviour described in this bug was a side effect of this. You can see this by trying to reproduce without numlock on.

fixed upstream

This upload fixes the bug:

 gtk+2.0 (2.10.10-0ubuntu1) feisty; urgency=low
 .
   * New upstream version:
     Bugs fixed:
     329450 Crash on IM switch ... (was already reported earlier)
     406757 crash in Movie Player: Souhaite lire un DVD ave...
     382565 GtkTextView invisible text crash
     402453 crash to IA__gdk_x11_window_set_user_time (Ubuntu: #82280)
     409101 invalid read to gtkicontheme.c insert_theme(), might caus...
     413032 Locking issue with xcb in IA__gdk_display_sync (Ubuntu: #88608)
     402131 Theme color scheme is sometimes ignored on theme switches
     405327 io-jpeg can return FALSE without setting a GError
     124045 GtkExpander should draw the focus around the arrow when t...
     143213 shorcut selector on gtkfilechooser use too much horizonta...
     151169 Filechooser comes up too big
     153785 Filechooser expands horizontally
     347106 tga images upside down
     356515 [a11y] Orca unable to read items in Evolution "Select a F...
     377164 Strange numbers in GtkRecentChooserMenu
     386618 Resizing columns need focusing first (Ubuntu: #62898)
     389765 Win32: Resizing a window does not repaint it often enough...
     393599 Previous and Next menus not active in a folder with *.ico...
            (Ubuntu: #88164)
     399907 Memory leak in gtk_page_setup dialog
     402565 [PATCH]GtkPrintBackendFile leaks string
     402806 GtkAboutDialog showing empty "contributors"
     403139 Leak reported by valgrind
     403255 gdk_pixbuf_loader_close returns TRUE but sets *error
     403409 Add a helpful comment on GtkCellRendererText:alignment
     403896 gtk+-2.10.9 fails to compile against win32api-3.8 due to ...
     405539 gdk_pixbuf_save() for PNG saver can return FALSE without ...
     405696 Make parent menu item insensitive if no items are to be s...
     409357 leak in color scheme code
     412221 Icons not working with Win32 file-system backend.
     412596 Setting the colour scheme property of GtkSettings has no ...
     413492 Minor build tweaks
     413664 Dragging tab greys out chat windows
     415645 Fix and clean up GtkCellRendererAccel
     310522 Buttons flicker and redraw slowly
     396899 glib mentions non-existing PATCH bugzilla keyword
     408018 GtkTextBuffer memory leak
     414875 Rendering the first icon triggers a style reset
     325477 Just make File Chooser window bigger
     414975 the popped up menu cannot have special theming
     331369 Menu short cuts do not work
     350988 crash with File Open in non-exisiting directory
     364946 crash in gtk_tree_model: Adding new account, or entering ...
     351671 textview should stop selecting when losing focus
     382904 Application crashed in gtk+
     385637 crash in testiconview
     396703 crash in testnouiprint
     396805 GtkTextView: crash on unsetting the GtkTextBuffer when in...
     410565 gnome-terminal crashes editing current profile
     335796 Gtk accelerator key event can't be passed to other widget...
     356515 [a11y] Orca unable to read items in Evolution "Select a F...
     416525 gtkfilesystemwin32.c: C99 declaration
     372449 no need to emph...