Your post is one year old, and nobody replied you...
I am having the same problem. apparently, according to the web site http://www.howtoforge.com/running-ub...ortable-ubuntu
it is probably because of the windows firewall, they say:
If you are using the Windows firewall, you might have to unblock two or three applications that are needed to run portable Ubuntu
but they don't say which are these applications...
Could somebody give an answer to that?
Thank you so much...