Simulink failed to open in R2015b

I just tried to start Simulink from R2015b (using the icon in the MATLAB ribbon and them by typing "simunlink". I get the message:

Can't reload 'C:\Program Files\MATLAB\R2015b\bin\win64\sl_graphical_classes.dll'

immediately.

Does anybody know what's going on? I used the DLL dependency for Win64 checker depends.exe against the above DLL and it claims that API-MS-WIN-APPMODEL-RUNTIME-L1-1-0.DLL is missing (amongst others). I have Microsoft Visual C++ Restributable for 2005, 2008, 2010, 2012, 2013, and 2015.

Any help appreciated.

Thanks,

Ender.