Arch Linux

And don't compile
$ abs
$ cd ~arch/abs/extra/xvidcap
$ makepkg -cifs
.....
capture.c:68:35: error: X11/extensions/shmstr.h: No such file or directory
capture.c: In function ‘paintMousePointer’:
capture.c:320: warning: suggest parentheses around operand of ‘!’ or change ‘&’ to ‘&&’ or ‘!’ to ‘~’
capture.c:352: warning: suggest parentheses around operand of ‘!’ or change ‘&’ to ‘&&’ or ‘!’ to ‘~’
capture.c: In function ‘XGetZPixmap’:
capture.c:608: warning: large integer implicitly truncated to unsigned type
capture.c: In function ‘XGetZPixmapSHM’:
capture.c:668: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘*’ token
capture.c:668: error: ‘req’ undeclared (first use in this function)
capture.c:668: error: (Each undeclared identifier is reported only once
capture.c:668: error: for each function it appears in.)
capture.c:669: error: ‘xShmGetImageReply’ undeclared (first use in this function)
capture.c:669: error: expected ‘;’ before ‘rep’
capture.c:675: error: ‘sz_xShmGetImageReq’ undeclared (first use in this function)
capture.c:675: error: ‘xShmGetImageReq’ undeclared (first use in this function)
capture.c:675: error: expected expression before ‘)’ token
capture.c:675: error: ‘X_ShmGetImage’ undeclared (first use in this function)
capture.c:693: error: ‘rep’ undeclared (first use in this function)
make[3]: *** [capture.o] Error 1
make[3]: Leaving directory `/home/robinho/arch/abs/extra/xvidcap/src/xvidcap-1.1.7/src'
make[2]: *** [all] Error 2
make[2]: Leaving directory `/home/robinho/arch/abs/extra/xvidcap/src/xvidcap-1.1.7/src'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/home/robinho/arch/abs/extra/xvidcap/src/xvidcap-1.1.7'
make: *** [all] Error 2
==> ERROR: Build Failed.
Aborting...

Could you please post a backtrace?

Maybe can help
http://bugs.gentoo.org/242680
http://bugs.gentoo.org/242678

And some gentoo's patch attached:
xvidcap-1.1.7-avutil.patch
xvidcap-1.1.7-ffmpeg-headers.patch
xvidcap-1.1.7-ffmpeg-trellis.patch

and Ubuntu:
01_configure.diff
03_ffmpeg.diff

Backtrace
#0 0x0000000000441511 in ?? ()
#1 0x00007ffff5706c27 in g_type_create_instance () from /usr/lib/libgobject-2.0.so.0
#2 0x00007ffff56ebb2c in g_object_constructor () from /usr/lib/libgobject-2.0.so.0
#3 0x00007ffff56ec94d in g_object_newv () from /usr/lib/libgobject-2.0.so.0
#4 0x00007ffff56ed6c5 in g_object_new_valist () from /usr/lib/libgobject-2.0.so.0
#5 0x00007ffff56ed81c in g_object_new () from /usr/lib/libgobject-2.0.so.0
#6 0x000000000044144e in xvc_server_object_new ()
#7 0x00000000004270aa in xvc_appdata_set_defaults ()
#8 0x0000000000439f4f in main ()

works here on i686. Anyway, I updated to -2 that builds with the new xextproto. try it.

With the same problem.
$ pacman -Qi xvidcap
Name : xvidcap
Version : 1.1.7-2
URL : http://xvidcap.sourceforge.net/
Licenses : GPL
Groups : None
Provides : None
Depends On : dbus-glib lame libxmu libglade
Optional Deps : None
Required By : None
Conflicts With : None
Replaces : None
Installed Size : 2588.00 K
Packager : Giovanni Scafora <giovanni@archlinux.org>
Architecture : x86_64
Build Date : Fri 15 Jan 2010 11:52:20 AM BRT
Install Date : Fri 15 Jan 2010 12:11:53 PM BRT
Install Reason : Explicitly installed
Install Script : No
Description : A small tool to capture things going on on an X-Windows display to either individual frames or an MPEG video

$ xvidcap

** (xvidcap:4083): WARNING **: Unable to connect to dbus: /usr/bin/dbus-launch terminated abnormally without any error message

** (xvidcap:4083): CRITICAL **: dbus_g_connection_register_g_object: assertion `connection != NULL' failed

** (xvidcap:4083): CRITICAL **: dbus_g_proxy_new_for_name: assertion `connection != NULL' failed

** (xvidcap:4083): CRITICAL **: dbus_g_proxy_call: assertion `DBUS_IS_G_PROXY (proxy)' failed
Segmentation fault

# Backtrace
$ gdb /usr/bin/xvidcap
#0 0x000000000041fca1 in ?? ()
#1 0x00007ffff6ec5c27 in g_type_create_instance () from /usr/lib/libgobject-2.0.so.0
#2 0x00007ffff6eaab2c in g_object_constructor () from /usr/lib/libgobject-2.0.so.0
#3 0x00007ffff6eab94d in g_object_newv () from /usr/lib/libgobject-2.0.so.0
#4 0x00007ffff6eac6c5 in g_object_new_valist () from /usr/lib/libgobject-2.0.so.0
#5 0x00007ffff6eac81c in g_object_new () from /usr/lib/libgobject-2.0.so.0
#6 0x000000000041fbde in xvc_server_object_new ()
#7 0x000000000040b665 in xvc_appdata_set_defaults ()
#8 0x000000000041b97b in main ()

works here on x86_64. Is the dbus daemon running? Are you starting a dbus session along with your DE/WM?

Sorry, it need change the Depends.
Please, put the dbus as dep, because is necessary dbus-launch to do it http://wiki.archlinux.org/index.php/Dbus#D-bus_Launch.

pacman -Qo /usr/bin/dbus-launch
/usr/bin/dbus-launch is owned by dbus 1.2.16-1

Thanks and sorry about the bug