ImageShack error: Unable to resolve hostname

This error occurs on a PC where I have installed two Windows 7 versions (one English, one German) on different hard drive partitions.
Under the English OS ImageShack upload plugin works fine, unter the German OS I get the error like mentioned in the subject.
ImageShack itself is running fine all the time, so it definitely is a problem with DO.

Do you have the latest version of Opus installed (10.1.0.0)? There were changes in Imageshack´s API, which most likely cause that problem, so
you might want to use the new version, which works fine with Imageshack.

Opus connects to exactly the same Imageshack URL (imageshack.us/index.php) regardless of which languages your copies of Windows and Opus as configured to use.

Assuming you have the same version of Opus installed on both partitions, the difference must be in the Opus proxy configuration and/or the Windows network/firewall configuration.

The hostname error even occurs when I try to retrieve update information from within the help menu of DO.
Deactivated the Windows Firewall temporarily, the error remains. There is no proxy configured.

I imported the settings from previous installations, that never caused any problems, but maybe this time?

PS: My version is 10.1.0.0

So Opus is being denied access to the Internet completely by something.

Can other things on that partition access the Internet?

What about anti-virus?

Should there be? What's the setup on the working partition?

(I'm talking about the proxy configuration within Opus's preferneces, not the Windows or Internet Explorer proxy configuration.)

No, that wouldn't cause this unless the old settings were already wrong.

Did it ever work on that partition?

If it started happening right after you updated Opus, and other programs can still access the Internet okay from that Windows install, then it's possible an anti-virus or similar tool has decided it doesn't recognise the new EXE and has decided to block it as a result.

The hint regarding the anti-virus program helped.
I checked for the rules and deleted everything related to DO.
Thanks!