It appears that a recent Java patch causes problems launching the IAS Viewer client and other Java-based software launched via Java Web Start. The update changed the location of the Java Web Start application so that the system opens the downloaded JNLP file as a text file, most likely with something called Dashcode. One of our system administrators found a solution on an Apple support discussion archive. You should only have to do this once to fix the problem:

1. Find any *.jnlp file in the Finder. These may be on your Desktop, or in a download folder, depending on how your web browser is configured.
2. Highlight the file by clicking on it, then select ‘Get Info’ from the File menu.
3. In the Open with: section, click on the popup menu and select ‘Other…’.
4. In the file chooser window that pops up, under Devices, pick the hard disk icon that corresponds to the name of your system hard disk (probably has the same name as your computer).
5. From there, select the System folder, then Library, then CoreServices, and scroll down to find the Java Web Start application, select it and click the ‘Add’ button. (Note, the location of Java Web Start application may differ on your system.)
6. Back in the Get Info window, click the button that says change all to apply this change to all of your JNLP files, then close the Get Info window.

When something tries to open a .jnlp file now, it should be properly handled by Java Web Start, launching the corresponding application.

Thanks to one of our twitter followers, @doug_ellison, for pointing out that many of you are having this problem!

Please note, we offer this for informative purposes, and you should make changes at your own discretion.