I've added a suppression for this already to http://code.google.com/p/winezeug/source/browse/trunk/valgrind/valgrind-supp...
It looks benign, but it's annoying because the suppression it needs is so wide. I wonder if the gcc bug on ubuntu 11.10 is why there's no useful backtrace there...
Syscall param writev(vector[...]) points to uninitialised byte(s) at writev (writev.c:51) by 0x40004: ??? Address 0x4598748 is 160 bytes inside a block of size 16,384 alloc'd at calloc (vg_replace_malloc.c:467) by XOpenDisplay (in /usr/lib/i386-linux-gnu/libX11.so.6.3.0) by x11drv_init_thread_data (x11drv_main.c:689) by thread_init_display (x11drv.h:580) by X11DRV_create_win_data (window.c:2030) by X11DRV_WindowPosChanging (window.c:2429) by set_window_pos (winpos.c:1951) by USER_SetWindowPos (winpos.c:2077) by SetWindowPos (winpos.c:2151) by show_window (winpos.c:1088) by ShowWindow (winpos.c:1186) by WIN_CreateWindowEx (win.c:1498) by CreateWindowExA (win.c:1550) by init (comboex.c:505) by func_comboex (comboex.c:598) by run_test (test.h:556) by main (test.h:624) Uninitialised value was created by a stack allocation at set_wm_hints (window.c:1128)