xvfb problem

I am new to this forum, I did have problem with the ststrunk_Control start, boot, option. it seem that the xvfb having a problem. when take look on the log file  xvfb_01.log, i found that the xvfb having some problem. So when it will be unsuccessful when running the ststrunk_Control start command.

mh@poise-desktop:~/siptosis/log$  more xvfb_01.log

Backtrace:
0: Xvfb (xorg_backtrace+0x37) [0x81b5b27]
1: Xvfb (0x8048000+0x17128a) [0x81b928a]
2: (vdso) (__kernel_rt_sigreturn+0x0) [0x30540c]
3: Xvfb (fbValidateGC+0x3ce) [0x806588e]
4: Xvfb (0x8048000+0xad8af) [0x80f58af]
5: Xvfb (ValidateGC+0x26) [0x81712f6]
6: Xvfb (0x8048000+0x1122bd) [0x815a2bd]
7: Xvfb (0x8048000+0x115b57) [0x815db57]
8: Xvfb (0x8048000+0x1654c) [0x805e54c]
9: /lib/i386-linux-gnu/libc.so.6 (__libc_start_main+0xf3) [0x14b113]
10: Xvfb (0x8048000+0x16861) [0x805e861]
Floating point exception at address 0x806588e

Caught signal 8 (Floating point exception). Server aborting

on this system,  ststrunk_Control config command is working fine, SipToSis_linux is also working fine.
my system is ubantu 11.10, all of the software are uptodate. I did try to search on this site and find more information regarding with the xvfb without success, so please help me on the issue.