Postscript-Viewer (ps, eps) (32-bit only)

Since the plugin is a 32-bit DLL it won't load at all in the 64-bit versions of Opus. A 64-bit DLL would need to be compiled (or some kind of 64-bit -> 32-bit proxy plugin made).

(The ActiveX plugin can do this, but uses a 64-bit to 32-bit proxy where necessary to load 32-bit components in 64-bit versions.)

64-bit users who want to display Postscript files should be able to do so by installing Ghostscript, from what I have read. The Ghostscript installer installs a viewer for Internet Explorer and the ActiveX + Preview + Office + Web plugin for Opus can be configured to take advantage of that: Go to Preferences - Plugins - Viewer Plugins, select the ActiveX plugin and click Configure, then add the .ps and .eps extensions under the Internet Explorer (32-bit) section. Those file extensions will then be displayed in the Opus viewer pane via IE.

Update: Turns out this is incorrect. Ghostview does not provide a viewer that works in Internet Explorer, despite its webpage suggesting it does.