Pronterface could not open port

Hello.
I need some advice, just installed everything like was in a nexdayreprap booklet. But when try to comunicate with the printer it says "connecting" all the time... when I click it once more said "python serialexception could not open port/access is denied"
What I'm doing wrong?
I tried to reinstall all once more but no help. Tried to change a port, update driver with older 2560...

my components are:
Funduino mega v3
ramps 1.4 ultimachine
a4988 drivers

Thanks in advance

I found a problem... thanks guys for your help

What did you find to solve the problem - I have the same issue that the port on 1 computer (Tosbiba portable Win10) has stopped opening the port connection (after a year without problem upgraded from Win 7 Professional) , but with another computer (Toshiba win7 ) works ok - so I know it is port connection on the Win 10 computer is the issue -

Your comport number may have changed, check in the device manager to see what it is.

Thanks,
The Device Manger is saying "USB Serial port ( com 3)"
Ponterface is saying it is trying to connect to Port 3
I have tried deleting the port, but when the plug reconnects it is still showing on the Devide Manager Port 3
The link cable should be OK as it works with the other computer (win 7)
AS further suggestions please?