Thank you for contacting Global Caché Technical Support Martin.
The issue with Firefox/Opera, and most Mozilla engine based browsers, is a known issue. Mozilla recently changed the way they handle form data and as a consequence broke the web pages on those browsers. This issue has been fixed in revision 3.0 of the firmware.
The Linux ping is a different size than Windows (Windows is 32 bytes). If you change the Linux ping size to 32 bytes, the GC-100 should respond to the ping.