You may need to test this in IE on Windows. Replicating it in a separate browser (which could have specific conditions on your system to allow it to work, while other network accesses are blocked or broken) isn't a valid test.
Interesting - I just tried the MusicEx manually on IE and got the below:
PrintWindows Network Diagnostics Publisher details
Issues found
The remote device or resource won't accept the connectionThe remote device or resource won't accept the connection
The device or resource (127.0.0.1) is not set up to accept connections on port "8080". Detected Detected
Contact your network administrator Completed
Issues found Detection details
5 The remote device or resource won't accept the connection Detected Detected
The device or resource (127.0.0.1) is not set up to accept connections on port "8080".
Contact your network administrator Completed
The computer or device you are trying to reach is available, but it doesn’t support what you’re trying to do. This might be a configuration issue or a limitation of the device.
Detection details Expand
InformationalNetwork Diagnostics Log
File Name: 4F1AE6F2-0E26-4576-8C1E-B35A305E41BE.Diagnose.0.etl
InformationalOther Networking Configuration and Logs
File Name: NetworkConfiguration.cab
Collection information
Computer Name: WWF-ONLINE-PC
Windows Version: 6.3
Architecture: x64
Time: 01 March 2015 09:28:36
Publisher details Expand
Windows Network Diagnostics
Detects problems with network connectivity.
Package Version: 1.0
Publisher: Microsoft Windows