I was having the same problem. Here's what I did:
1) Download the TightVNC Java viewer from tightvnc.com (tightvnc-1.2.8_javabin.zip as of today).
2) Rename the original vncviewer.jar file (/drive0/opt/khttpd/charcoalgray99/jar/vncviewer.jar) to vncviewer.jar.orig (if you want a backup)
3) Drop the VncViewer.jar from TightVNC into the jar directory and rename to match the original jarfile's name -- case sensitive (I renamed VncViewer.jar to vncviewer.jar)
4) Modify jscripts.js (/drive0/opt/khttpd/charcoalgray99/js/jscripts.js) such that parameters which TightVNC likes are passed to the applet. The first few lines of the drawFascia(url) function (approximately line 189) should look like this:
function drawFascia(url)
{
if (useVNC == true)
{
document.write("<applet CODE=VncViewer.class ARCHIVE=\"/drive0/opt/khttpd/charcoalgray99/jar/vncviewer.jar\" WIDTH=\"300\" HEIGHT=\"93\">");
document.write("<param name=\"PORT\" value=\"5900\"/>");
document.write("<param name=\"PASSWORD\" value=\"\"/>");
document.write("<param name=\"Encoding\" value=\"Raw\"/>");
document.write("<param name=\"Restricted colors\" value=\"Yes\"/>");
document.write("<param name=\"Show controls\" value=\"No\"/>");
document.write("</applet>");
}
.... function continues, but I do not list it here.
TightVNC's applet code seems to work better than ATT's when navigating between pages, etc.
I am using J2SE 1.4 with the plugin and it's pretty solid. Just don't try to connect twice (as wfaulk has mentioned) or you will crash the vnc server and will need to restart it.
The parameters I added were just my first guesses, so other combinations will likely work also. Here are my guesses and why I chose them:
PASSWORD="" -- don't use authentication
Encoding="Raw" -- guessed based on the att java client patchfile
"Restricted colors"="Yes" -- empegVNC doesn't like 24-bit connections
"Show controls"="No" -- don't add the GUI buttons (Options, etc) to the TightVNC client applet