There are a number of initiatives underway to provide better troubleshooting tools and diagnostics for the Siebel Plug-in.  We'll make sure that we announce those as soon as they are available.

In the meantime, I wanted to make everyone aware of an existing Wiki that provides troubleshooting tips/techniques, as well as a list of common issues.  Unfortunately, this Wiki is only accessbile to internal Oracle employees.  The wiki is located here.

In addition to the troubleshooting information, one of the more valuable aspects of the Wiki is a listing of the latest requried patches for the Siebel Plug-in.  This list is maintained by our Engineering staff, and reflects the latest information on required patches for all current releases (i.e., 12c, 11g, and 10.2.0.5).  The list of patches can be accessed here.