Here's how I ran into this problem...

Liferay has a tag library JAR named util-taglib.jar that gets added to every hot-deployed WAR, whether it needs it or not.

Well anyway, inside util-taglib.jar there is a file named:
    META-INF/liferay-portlet-ext.tld

Which has the following DTD specified:
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">

Now I realize this is an ancient tag library DTD, and we need to update that, however, when the ICEfaces TlDLocationsCache was trying to extract the TLD file and parse it with an XML parser, it couldn't find the ancient web-jsptaglibrary_1_1.dtd file in the com/icesoft/jasper/ ClassPath. (The only one there is web-jsptaglibrary_1_2.dtd).

Like I said, the XML parser couldn't validate the tag library against this ancient DTD, and so the com.icesoft.jasper.xmlparser.CachedEntityResolver class threw this exception:

                    throw new SAXException(
                            Localizer.getMessage(
                                    "jsp.error.internal.filenotfound",
                                    resourcePath));

Now, the Localizer class is supposed to load up a message bundle (according to the locale of the user I guess), and substitute the resourcePath (/com/icesoft/jasper/web-jsptaglibrary_1_1.dtd) into the message.

Well, the whole resourceBundle stuff is totally commented out of the Localizer class, and therefore, it never gets substituted.

Recommend that ICEsoft implement/re-implement the resourceBundle method, or otherwise, simply concatenate all of the parameters to the message, rather than ignore them. Right now the "Localizer" class doesn't localize at all.