Skype Problem

[#1]

Hi Guys
           Something strange for the last couple of months with Skype and my connection,
running windows 7 home premium 64bt and i have tried every version of Skype but i still cannot share my screen, Skype works ok apart from that but when i try to share my screen it says that there is no network connection even though Skype is working as im talking to my friends, the only way around it is to change the port number for incoming connections, but this lasts only a minute before kicking me out,
Over the last 6 months i have done clean computer installs but still get the  no network connection, now here is the strange part if i connect to another ISP connection all works fine as it should and that`s why i ask the question here and not on Skype forum, its the same for desktop and laptop not just one unit, will try to change my Netgear DG834PN as a last resort as im now void of new ides`s after 6 months so any help appreciated as i have done all the obvious stuff,
Update just changed router but still no joy
Regards Binzy

[#2]

Sounds like you might have the plusnet firewall enabled on your connection. It just kinda turned up one day a few years back lol
Login to the portal and see if it's turned on. If it is, thats quite possibly affecting your skype.
This is where to find it:

[#3]

Hi    7up
Thanks for the excellent detailed reply but the firewall is off, And as my computers work ok on other ISP provider i tested them on i think the answer my well lay with Plusnet and not my configuration as ive tried everything on my side, But ive not heard of others reporting problem like this on here before,
Regards binzy