All stars show a triangle around them

Please reset Stellarium's setting (restore default), if it not help the try update drivers on graphics card. Please in any case attach log.txt.

I have the same problem - Using Stellarium 0.12.0 on Windows-8 64 with an AMD phenom processor, and mboard with an ATI 4200 onboard graphics.
It displays large triangles around larger (or brighter) objects in sky.

I also have a laptop with Win-8 on it, and a 32-bit Win-7 system. I have not tried 0.12.0 on either of these yet.
I'll let you know how 0.12.0 behaves on these two systems
FWIW, Stellarium 0.11 worked fin on this PC with Win-7 before I upgraded to Win-8.

Hmmm... upon examining the log below, first thing I notice is "Unsupported Windows version" LOL!
I'll let you deal with the rest! ;-)

2013-03-18T00:57:56
Unsupported Windows version
Compiled using MinGW GCC 4.6.1
Qt runtime version: 4.8.2
Qt compilation version: 4.8.2
Addressing mode: 64-bit
Total memory: 12031 MB (unreliable)
Total virtual memory: 8388607 MB (unreliable)
Physical memory in use: 16%
Processor speed: 3300 MHz
Processor name: AMD Phenom(tm) II X2 560 Processor
Processor speed: 3300 MHz
Processor name: AMD Phenom(tm) II X2 560 Processor
C:\Program Files\Stellarium\stellarium.exe
 -------------------------------------------------------
[ This is Stellarium 0.12.0 - http://www.stellarium.org ]
[ Copyright (C) 2000-2013 Fabien Chereau et al ]
 -------------------------------------------------------
Writing log file to: "C:/Users/aqk/AppData/Roaming/Stellarium/log.txt"
File search paths:
  0 . "C:\Users\aqk\AppData\Roaming\Stellarium"
  1 . "."
Config file is: "C:\Users\aqk\AppData\Roaming\Stellarium/config.ini"
Going to initialize the OpenGL 2 renderer
OpenGL supported version: "1.1.0"
Qt GL paint engine is: "OpenGL"
StelQGL2Renderer::init : Failed because Qt paint engine is not OpenGL2
If paint engine is OpenGL3 or higher, this code needs to be updated
Failed to initialize the OpenGL 2 renderer, falling back to the OpenGL 1 renderer
OpenGL supported version: "1.1.0"
Qt GL paint engine is: "OpenGL"
GL vendor is "Microsoft Corporation"
GL renderer is "GDI Generic"
Cache directory is: "C:\Users\aqk\AppData\Local\stellarium\stellarium\cache"
Sky language is "en_US"
Application language is "en_US"
Loading Solar System data ...
Loaded 74 / 74 planet orbits from "C:\Users\aqk\AppData\Roaming\Stellarium/data/ssystem.ini"
Loading star data ...
"Loading "./stars/default/stars_0_0v0_1.cat": 0_0v0_1; 5013"
"Loading "./stars/default/stars_1_0v0_1.cat": 1_0v0_1; 21999"
"Loading "./stars/default/stars_2_0v0_1.cat": 2_0v0_1; 151416"
"Loading "./stars/default/stars_3_1v0_0.cat": 3_1v0_0; 434064"
Finished loading star catalogue data, max_geodesic_level: 3
navigation/preset_sky_time is a double - treating as jday: 2.45151e+06
Loaded 10051 NGC records
Loading NGC name data ...
Loaded 288 / 288 NGC name records successfully
Loading star names from "./skycultures/western/star_names.fab"
Loaded 230 / 230 common star names
Loading star names from "./stars/default/name.fab"
Loaded 3215 / 4359 scientific star names
Loaded 88 / 88 constellation records successfully for culture "western"
Loaded 85 / 85 constellation art records successfully for culture "western"
Loaded 89 / 89 constellation names
Loading constellation boundary data ...
Loaded 782 constellation boundary segments
Not using any viewport effect
Creating GUI ...
Loading shortcuts...
Loaded plugin "Oculars" .
Ocular plugin - press Command-O to toggle eyepiece view mode. Press ALT-o for configuration.
Oculars::validateIniFile ocular.ini exists at: "C:\Users\aqk\AppData\Roaming\Stellarium/modules/Oculars/ocular.ini" . Checking version...
Oculars::validateIniFile found existing ini file version 2
Loaded plugin "Satellites" .
Satellites::getJsonFileVersion() version from file: "0.7.3"
Satellites::init using satellite.json file: "C:\Users\aqk\AppData\Roaming\Stellarium/modules/Satellites/satellites.json"
Satellite has invalid orbit: "CZ-4B R/B" "28471"
Loaded plugin "SolarSystemEditor" .
Using the ssystem.ini file that already exists in the user directory...
Loaded plugin "TimeZoneConfiguration" .
OpenGL error detected at "drawWindow() start" : "GL_INVALID_ENUM"
OpenGL error detected at "drawWindow() start" : "GL_INVALID_ENUM"
OpenGL error detected at "drawWindow() start" : "GL_INVALID_ENUM"
   ...and this error repeats for a couple of hundred lines.....

You need install drivers for graphics card.

Win-8 currently uses its default drivers - WDDM V1.1

I've DLed the AMD/ATI catalyst control center (CCC) that apparently has a driver for win-8 in it. Will try it tomorrow.

In meantime I have discovered I already had a Launchpad ID (so many ids!) - "ubu@..."

  "ubu@..." - the one I'm logged in with now. Will see if I can somehow get rid of the other "tech-8" ID.

   Thanx.
   -aqk