Enable/Disable GUI on bootup

[Tim Alberts]

Anthony Messina wrote ..
> also, booting into runlevel 3 then doing "startx" is not the same as 
> booting into runlevel 5: other services that are only configured to run
> in runlevel 5 don't start that way.
> 
> if you need to boot to runlevel 3, then switch to runlevel 5, do 
> "telinit 5" from the runlevel 3 command prompt.
> 
> man telinit

Why would 'telinit 3' from the KDE desktop terminal window cause my computer to hang?
Should I not be doing this from within KDE?