There's a ViewpointMediaPlayer version for Mozilla/5.0 Firebird?

A) Just check in "C:\Program Files\Viewpoint\Viewpoint Media Player"
if the files "npViewpoint.dll" and "npViewpoint.xpt" exist.

If they do exist just copy them in your Firebird's plugins folder. And it should work.

If you don't have these files, just get
"ftp://ftp.netscape.com/pub/netscape7/english/7.1/windows/win32/jgksyc/viewpoint.zip"
from netscape 7.1, unzip, install then restart from A)