Please upload a Xorg log file.

Examples on an installed system:
/var/log/Xorg.0.log
/var/log/Xorg.0.log.old

And in case of anaconda (install media):
/tmp/X.log

Thanks.

Created attachment 752954 [details]
Xorg.0.log

As asked adding Xorg.0.log

From Comment #2 attachment:

[   182.694] (EE) 
[   182.694] (EE) Backtrace:
[   182.694] (EE) 0: /usr/bin/Xorg (OsLookupColor+0x138) [0x80b9048]
[   182.706] (EE) 1: ? (?+0x138) [0xb77b9543]
[   182.706] (EE) 2: /usr/lib/xorg/modules/extensions/libglx.so (_init+0x4be7d) [0xb76dbbed]
[   182.707] (EE) 3: /usr/lib/xorg/modules/drivers/sis_drv.so (_init+0x3794a) [0xb76b31ca]
[   182.707] (EE) 4: /usr/lib/xorg/modules/drivers/sis_drv.so (_init+0x259ad) [0xb768f1dd]
[   182.708] (EE) 5: /usr/lib/xorg/modules/libexa.so (exaMoveOutPixmap+0x139c) [0xb75f852c]
[   182.709] (EE) 6: /usr/lib/xorg/modules/libexa.so (exaMoveOutPixmap+0x18d2) [0xb75f9182]
[   182.709] (EE) 7: /usr/lib/xorg/modules/libexa.so (exaMoveOutPixmap+0x1a97) [0xb75f94c7]
[   182.710] (EE) 8: /usr/lib/xorg/modules/libexa.so (exaMoveOutPixmap+0x22da) [0xb75f9fba]
[   182.711] (EE) 9: /usr/lib/xorg/modules/libexa.so (exaWaitSync+0xf0) [0xb75f6080]
[   182.711] (EE) 10: /usr/lib/xorg/modules/libexa.so (exaMoveOutPixmap+0x5530) [0xb76006a0]
[   182.712] (EE) 11: /usr/lib/xorg/modules/libexa.so (exaMoveOutPixmap+0x5f68) [0xb7601e78]
[   182.712] (EE) 12: /usr/bin/Xorg (miCopyRegion+0x184) [0x81dd8c4]
[   182.713] (EE) 13: /usr/bin/Xorg (miDoCopy+0x500) [0x81ddf10]
[   182.713] (EE) 14: /usr/lib/xorg/modules/libexa.so (exaMoveOutPixmap+0x3ff2) [0xb75fdf42]
[   182.714] (EE) 15: /usr/bin/Xorg (DamageRegionProcessPending+0x376e) [0x8186d4e]
[   182.714] (EE) 16: /usr/bin/Xorg (dixDestroyPixmap+0x9f3) [0x8077db3]
[   182.715] (EE) 17: /usr/bin/Xorg (SendErrorToClient+0x3fd) [0x807bd8d]
[   182.715] (EE) 18: /usr/bin/Xorg (_init+0x46ad) [0x806d16d]
[   182.737] (EE) 19: /lib/libc.so.6 (__libc_start_main+0xf5) [0x491f3865]
[   182.737] (EE) 20: /usr/bin/Xorg (_start+0x21) [0x80692aa]
[   182.737] (EE) 
[   182.737] (EE) Segmentation fault at address 0x0
[   182.737] 
Fatal server error:
[   182.737] Caught signal 11 (Segmentation fault). Server aborting
[   182.737] 
[   182.737] (EE) 
Please consult the Fedora Project support 
	 at http://wiki.x.org
 for help. 
[   182.737] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[   182.737] (EE)

Please put an 'lspci -nn | grep VGA' output

$ lspci -nn | grep VGA
01:00.0 VGA compatible controller [0300]: Silicon Integrated Systems [SiS] 661/741/760 PCI/AGP or 662/761Gx PCIE VGA Display Adapter [1039:6330]

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bug reports from releases that are no longer maintained. At that time
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The bug is still preset in fedora 20

This message is a reminder that Fedora 20 is nearing its end of life.
Approximately 4 (four) weeks from now Fedora will stop maintaining
and issuing updates for Fedora 20. It is Fedora's policy to close all
bug reports from releases that are no longer maintained. At that time
this bug will be closed as EOL if it remains open with a Fedora  'version'
of '20'.

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, simply change the 'version' 
to a later Fedora version.

Thank you for reporting this issue and we are sorry that we were not 
able to fix it before Fedora 20 is end of life. If you would still like 
to see this bug fixed and are able to reproduce it against a later version 
of Fedora, you are encouraged  change the 'version' to a later Fedora 
version prior this bug is closed as described in the policy above.

Although we aim to fix as many bugs as possible during every release's 
lifetime, sometimes those efforts are overtaken by events. Often a 
more recent Fedora release includes newer upstream software that fixes 
bugs or makes them obsolete.

Fedora 20 changed to end-of-life (EOL) status on 2015-06-23. Fedora 20 is
no longer maintained, which means that it will not receive any further
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of
Fedora please feel free to reopen this bug against that version. If you
are unable to reopen this bug, please file a new report against the
current release. If you experience problems, please add a comment to this
bug.

Thank you for reporting this bug and we are sorry it could not be fixed.