Black screen after closing/tabbing out of portal 2

[Riptide]

Hey guys,

after exciting portal 2/tabbing out of portal 2 my desktop is turning black. pressing alt + f4, tabbing in again or trying to open the task manager via crtl + alt + del doenst work. any ideas?

MB Asus H97M-E Intel H97 So. 1150 Dual Channel DDR3 mATX Retail
CPU Intel Core i5 4460 4x 3.20 GHz So. 1150
VGA 4096MB Gigabyte Radeon R9 380 Gaming G1
DDR3 16GB (2x 4096, 1x 8192) HyperX Savage 1600 DIMM CL9

[Detnom]

Having the same issue.