If Matlab is very slow to start or stuck in the initializing state or unable to quit, it could be because the LM_LICENSE_FILE is set. And it’s usually set because other programs need it set, so the solution of deleting that variable won’t work. Instead, change the shortcut that starts the program to:
C:\MATLAB\R2013b\matlab.exe -c "C:\MATLAB\R2013b\licenses\license_file.dat"
That will cause it to just look at the license file specified and not do anything with LM_LICENSE_FILE.