i hope if you are the real admin of jriver, you are supposed to check this issue further.
Sorry if no one made it clear before: Media Center's installer
does not contain a file, and
does not install a file, called w3gzg.dll in the System directory or anywhere else.
If you don't believe me, you can easily check this yourself. The installer EXE, like most installer packages, is just an executable ZIP file. Download a copy from here and extract it with a ZIP application like 7zip, rather than "running" it. Look inside the contents of the extracted installer.
There is no w3gzg.dll in the installer.They're sure. Hendrik is one of the developers of MC. I'm sure, because I just looked.
So, then... That presents three possible causes:
1. Comodo is wrong, and is seeing a temporary file name or something like that.
2. Some other application tried to install that file, and Comodo wrongly attibuted the behavior to Media Center.
3. Comodo is showing incorrect information and there is no w3gzg.dll file at all.
Since I couldn't find any clear references to w3gzg.dll on the Internet at all, and because the filename changes (as you stated), that leads me to believe this is some kind of randomly-generated file name. Malware often tries to install randomly named DLLs in the System directory. Temp files also often have randomly generated names.
In any case, if Comodo's beef is with some file called w3gzg.dll: that isn't JRiver's file. Since it is their error message, you need to ask them about it, to see if they can give you some kind of guidance on where that error might be coming from. I'm sure JRiver would be happy to supply them with a copy of the installer and a license key, if contacted.