Cant connect to printer?? (no replies)

hi, i have a prusa mendel iteration 2 running ramps 1.4 / mega 2560 using pronterface and all was looking well, even had some prints of out it, however everytime i try to connect now i get the following message

Hotend temperature presets updated, pla:185, abs:230
Connecting...
Traceback (most recent call last):
File "C:\Users\3DPartsUK\Desktop\RepRrap\kliment-Printrun-d9a3363\kliment-Prin
trun-d9a3363\pronterface.py", line 1567, in connect
self.p.connect(port,baud)
File "C:\Users\3DPartsUK\Desktop\RepRrap\kliment-Printrun-d9a3363\kliment-Prin
trun-d9a3363\printcore.py", line 76, in connect
self.printer=Serial(self.port,self.baud,timeout=5)
File "C:\Python27\lib\site-packages\serial\serialwin32.py", line 30, in __init
__
SerialBase.__init__(self, *args, **kwargs)
File "C:\Python27\lib\site-packages\serial\serialutil.py", line 260, in __init
__
self.open()
File "C:\Python27\lib\site-packages\serial\serialwin32.py", line 56, in open
raise SerialException("could not open port %s: %s" % (self.portstr, ctypes.W
inError()))
serial.serialutil.SerialException: could not open port COM6: [Error 2] The syste
m cannot find the file specified.


any ideas?