I also see this problem, for some reason after a while xvidcap did stop working.
The problem is hard reproducable, I simply start xvidcap press record and the GUI disapears. The command line shows the following output:
andres@schnecke:~$ xvidcap
[mpeg4 @ 0x8de85c0]removing common factors from framerate
[oss @ 0x8e44f30]/dev/dsp: Device or resource busy
*** glibc detected *** xvidcap: double free or corruption (!prev): 0x08e46f00 ***
======= Backtrace: =========
/lib/tls/i686/cmov/libc.so.6[0x791ff1]
/lib/tls/i686/cmov/libc.so.6[0x7936f2]
/lib/tls/i686/cmov/libc.so.6(cfree+0x6d)[0x7967cd]
/usr/lib/i686/cmov/libavformat.so.52(av_open_input_stream+0x15c)[0x8fc60c]
======= Memory map: ========
00110000-004c8000 r-xp 00000000 08:05 17729      /usr/lib/libgtk-x11-2.0.so.0.1800.3
004c8000-004c9000 ---p 003b8000 08:05 17729      /usr/lib/libgtk-x11-2.0.so.0.1800.3
004c9000-004cd000 r--p 003b8000 08:05 17729      /usr/lib/libgtk-x11-2.0.so.0.1800.3
004cd000-004cf000 rw-p 003bc000 08:05 17729      /usr/lib/libgtk-x11-2.0.so.0.1800.3
004cf000-004d1000 rw-p 00000000 00:00 0 
004d1000-00563000 r-xp 00000000 08:05 17773      /usr/lib/libgdk-x11-2.0.so.0.1800.3
00563000-00565000 r--p 00092000 08:05 17773      /usr/lib/libgdk-x11-2.0.so.0.1800.3
00565000-00566000 rw-p 00094000 08:05 17773      /usr/lib/libgdk-x11-2.0.so.0.1800.3
00566000-005ac000 r-xp 00000000 08:05 18111      /usr/lib/libpango-1.0.so.0.2600.0
005ac000-005ad000 r--p 00045000 08:05 18111      /usr/lib/libpango-1.0.so.0.2600.0
005ad000-005ae000 rw-p 00046000 08:05 18111      /usr/lib/libpango-1.0.so.0.2600.0
005ae000-005ea000 r-xp 00000000 08:05 17216      /usr/lib/libgobject-2.0.so.0.2200.3
005ea000-005eb000 r--p 0003b000 08:05 17216      /usr/lib/libgobject-2.0.so.0.2200.3
005eb000-005ec000 rw-p 0003c000 08:05 17216      /usr/lib/libgobject-2.0.so.0.2200.3
005ec000-005f0000 r-xp 00000000 08:05 17885      /usr/lib/libgthread-2.0.so.0.2200.3
005f0000-005f1000 r--p 00003000 08:05 17885      /usr/lib/libgthread-2.0.so.0.2200.3
005f1000-005f2000 rw-p 00004000 08:05 17885      /usr/lib/libgthread-2.0.so.0.2200.3
005f2000-006a7000 r-xp 00000000 08:05 1730920    /lib/libglib-2.0.so.0.2200.3
006a7000-006a8000 r--p 000b4000 08:05 1730920    /lib/libglib-2.0.so.0.2200.3
006a8000-006a9000 rw-p 000b5000 08:05 1730920    /lib/libglib-2.0.so.0.2200.3
006a9000-006be000 r-xp 00000000 08:05 1746313    /lib/tls/i686/cmov/libpthread-2.10.1.so
006be000-006bf000 r--p 00014000 08:05 1746313    /lib/tls/i686/cmov/libpthread-2.10.1.so
006bf000-006c0000 rw-p 00015000 08:05 1746313    /lib/tls/i686/cmov/libpthread-2.10.1.so
006c0000-006c2000 rw-p 00000000 00:00 0 
006c2000-006cb000 r-xp 00000000 08:05 417881     /usr/lib/i686/cmov/libavdevice.so.52.1.0
006cb000-006cc000 r--p 00008000 08:05 417881     /usr/lib/i686/cmov/libavdevice.so.52.1.0
006cc000-006cd000 rw-p 00009000 08:05 417881     /usr/lib/i686/cmov/libavdevice.so.52.1.0
006cd000-006f8000 r-xp 00000000 08:05 417891     /usr/lib/i686/cmov/libswscale.so.0.7.1
006f8000-006f9000 r--p 0002a000 08:05 417891     /usr/lib/i686/cmov/libswscale.so.0.7.1
006f9000-006fa000 rw-p 0002b000 08:05 417891     /usr/lib/i686/cmov/libswscale.so.0.7.1
006fa000-00706000 r-xp 00000000 08:05 417859     /usr/lib/i686/cmov/libavutil.so.49.15.0
00706000-00707000 r--p 0000b000 08:05 417859     /usr/lib/i686/cmov/libavutil.so.49.15.0
00707000-00708000 rw-p 0000c000 08:05 417859     /usr/lib/i686/cmov/libavutil.so.49.15.0
00708000-0070b000 rw-p 00000000 00:00 0 
0070b000-0070d000 r-xp 00000000 08:05 19042      /usr/lib/libXdamage.so.1.1.0
0070d000-0070e000 rw-p 00001000 08:05 19042      /usr/lib/libXdamage.so.1.1.0
0070e000-00725000 r-xp 00000000 08:05 18930      /usr/lib/libXmu.so.6.2.0
00725000-00726000 r--p 00016000 08:05 18930      /usr/lib/libXmu.so.6.2.0
00726000-00727000 rw-p 00017000 08:05 18930      /usr/lib/libXmu.so.6.2.0
00727000-00865000 r-xp 00000000 08:05 1746262    /lib/tls/i686/cmov/libc-2.10.1.so
00865000-00866000 ---p 0013e000 08:05 1746262    /lib/tls/i686/cmov/libc-2.10.1.so
00866000-00868000 r--p 0013e000 08:05 1746262    /lib/tls/i686/cmov/libc-2.10.1.so
00868000-00869000 rw-p 00140000 08:05 1746262    /lib/tls/i686/cmov/libc-2.10.1.so
00869000-0086c000 rw-p 00000000 00:00 0 
0086c000-00887000 r-xp 00000000 08:05 16728      /usr/lib/libatk-1.0.so.0.2809.1
00887000-00888000 r--p 0001b000 08:05 16728      /usr/lib/libatk-1.0.so.0.2809.1
00888000-00889000 rw-p 0001c000 08:05 16728      /usr/lib/libatk-1.0.so.0.2809.1
00889000-008b0000 r-xp 00000000 08:05 18113      /usr/lib/libpangoft2-1.0.so.0.2600.0
008b0000-008b1000 r--p 00027000 08:05 18113      /usr/lib/libpangoft2-1.0.so.0.2600.0
008b1000-008b2000 rw-p 00028000 08:05 18113      /usr/lib/libpangoft2-1.0.so.0.2600.0
008b2000-008ca000 r-xp 00000000 08:05 18203      /usr/lib/libgdk_pixbuf-2.0.so.0.1800.3
008ca000-008cb000 r--p 00017000 08:05 18203      /usr/lib/libgdk_pixbuf-2.0.so.0.1800.3
008cb000-008cc000 rw-p 00018000 08:05 18203      /usr/lib/libgdk_pixbuf-2.0.so.0.1800.3
008cc000-008d7000 r-xp 00000000 08:05 18112      /usr/lib/libpangocairo-1.0.so.0.2600.0
008d7000-008d8000 r--p 0000a000 08:05 18112      /usr/lib/libpangocairo-1.0.so.0.2600.0
008d8000-008d9000 rw-p 0000b000 08:05 18112      /usr/lib/libpangocairo-1.0.so.0.2600.0
008d9000-008dc000 r-xp 00000000 08:05 17884      /usr/lib/libgmodule-2.0.so.0.2200.3
008dc000-008dd000 r--p 00002000 08:05 17884      /usr/lib/libgmodule-2.0.so.0.2200.3
008dd000-008de000 rw-p 00003000 08:05 17884      /usr/lib/libgmodule-2.0.so.0.2200.3
008e0000-00988000 r-xp 00000000 08:05 417864     /usr/lib/i686/cmov/libavformat.so.52.31.0
00988000-00989000 r--p 000a7000 08:05 417864     /usr/lib/i686/cmov/libavformat.so.52.31.0
00989000-0098f000 rw-p 000a8000 08:05 417864     /usr/lib/i686/cmov/libavformat.so.52.31.0
0098f000-009db000 rw-p 00000000 00:00 0 
009db000-009dd000 r-xp 00000000 08:05 1730930    /usr/lib/libXcomposite.so.1.0.0
009dd000-009de000 r--p 00001000 08:05 1730930    /usr/lib/libXcomposite.so.1.0.0
009de000-009df000 rw-p 00002000 08:05 1730930    /usr/lib/libXcomposite.so.1.0.0
009e0000-009f6000 r-xp 00000000 08:05 19387      /usr/lib/libglade-2.0.so.0.0.7
009f6000-009f7000 r--p 00015000 08:05 19387      /usr/lib/libglade-2.0.so.0.0.7
009f7000-009f8000 rw-p 00016000 08:05 19387      /usr/lib/libglade-2.0.so.0.0.7
009f8000-00a00000 r-xp 00000000 08:05 18106      /usr/lib/libXrender.so.1.3.0
00a00000-00a01000 r--p 00007000 08:05 18106      /usr/lib/libXrender.so.1.3.0
00a01000-00a02000 rw-p 00008000 08:05 18106      /usr/lib/libXrender.so.1.3.0
00a02000-00a04000 r-xp 00000000 08:05 19056      /usr/lib/libXinerama.so.1.0.0
00a04000-00a05000 rw-p 00001000 08:05 19056      /usr/lib/libXinerama.so.1.0.0Aborted

Any idea how I can get around this?
Thanks for your help.
Michael