[Qgis-user] Heatmap invbisible

[Björn Freitag]

Hi folks!

im new to qgis and i have a problem with heatmaps i cant really solve.

i took GIS data from => 
http://www.cityofchicago.org/city/en/depts/doit/supp_info/gis_data.html
i took crime Data from => 
https://data.cityofchicago.org/Public-Safety/Crimes-2001-to-present/ijzp-q8t2

in my project i made an deliminated text layer with crime data. all went 
ok. I tried to generate a heatmap out of crime data (arested or not 
arested => not arested) but it did not work as expected.
the new layer with the heatmap is visible as a layer, but not with its 
data/heatmap on the map. When i open the layer properties i can see a 
mini heatmap.  if i change the color or something else, the mini map is 
even gone.

screenshot: http://www.bilder-upload.eu/show.php?file=ec1cba-1429951395.png

can someone give me a hint for that problem?

Here are my specs:

qgis 64 bit 2.8.1

xeon 1240v3
16 GB Ram
256 gb SSD
win7 64bit
nvidia gtx970 4gb