Generally speaking, no, this is not a Cross Site Scripting (XSS) issue.

You can have two problems:

 1. If the attacker control the first bytes of the output, the
    Rosetta Flash attack can be used to trigger a Cross Site Scripting (XSS).
    But if you start the output with `/*`, like you said you do, I can not see any risk;
 2. Outdated browsers (e.g.: IE 7) have content-sniffing issues, so even you setting the content-type of your page to `text/javascript`, an attacker could trick the browser to execute your page as HTML. Nowadays, this type of attack is very rare.
Use the following header to become safer.

    

> X-Content-Type-Options: nosniff