I just received an email from our IT/Network support which bears closer investigation.
We have experienced issues in PCs where users have done SKYPE upgrades - we don't know which version at this time but it manifests itself in not letting the users browse the internet. The only internet application which works is Skype. Seems like the latest version of Skype affects both Outlook and IE - while Skype is running neither can connect to the internet. Turn off Skype off and they work fine.
We don't believe there is a Spyware/Malware/Virus issue here - we suspect it's more to do with a Microsoft update than the Skype application itself but we’re still investigating.
Watch this space - more to follow hopefully.