Configured "Server Base Url" under Administration/General Configuration/Site
Configuration as "https://volkswagen-tui-portal.web.vwg/wikis/confluence"

Put confluence behind a reverse proxy (WebSeal) which performs a URL mapping
like the following:
From public URL:
https://volkswagen-tui-portal.web.vwg/wikis/confluence/dashboard.action
To non-public URL:
https://devwagwoc38y650.wob.vw.vwg/confluence/dashboard.action

Steps to reproduce the problem
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
To reproduce the error I pass the following steps:

• Point your browser the public Confluence URL:
  https://volkswagen-tui-portal.web.vwg/wikis/confluence
• Login
• Go to Page "Dashboard" (necessary since this isn't the site homepage
  in our installation).
• Click on the "My" spaces link.
• An error message from the reverse proxy is shown:
  "The Access Manager WebSEAL server cannot find any resource matching
  the requested URL: /confluence/dashboard.action?spacesSelectedTab=my"

Investigating the problem
^^^^^^^^^^^^^^^^^^^^^^^^^
The Problem can be tracked down as follows:
In the source-code of the dashboard page the "My"-Link is defined this way:
<a href="#" onClick="gotoUrl('/confluence/dashboard.action?spacesSelectedTab=my'); return false;">My</a>
When you click the My-Link the following URL gets called:
https://volkswagen-tui-portal.web.vwg/confluence/dashboard.action?spacesSelectedTab=my

You can see the cause of the problem here:
The URL given in the Javascript-gotoUrl-command leads to the wrong path after
the host name because the path component "wikis" is missing. The correct link
should be
<a href="#" onClick="gotoUrl(' https://volkswagen-tui-portal.web.vwg/wikis/confluence/dashboard.action?spacesSelectedTab=my'); return false;">My</a>
that is, the configured property "server base url" should appear in it.

Where does the wrong URL come from?
When you search for the Velocity template which stands behind the dashboard
page, you'll find the following file:
confluence-2.2.9-source\confluence\src\webapp\template\xhtml\spacelist.vm

In this spacelist.vm-file you'll find our link definition mentioned above in
line 30:
... <a href="#" onClick="gotoUrl('${baseurl}spacesSelectedTab=my'); ...

As you can see, our problematic URL part stems from the property ${baseurl}.

Where gets the property baseurl defined?
A little more research leads to this java class:
/Confluence-2.2.9/src/java/com/atlassian/confluence/renderer/radeox/macros/AbstractHtmlGeneratingMacro.java

In this class "AbstractHtmlGeneratingMacro" there is a method called
"buildBaseUrl" which creates the baseurl used during page generation.
Unfortunately, this method creates the baseurl by using the incoming
HttpServletRequest's method "getRequestURI()". The returned URI is the one used
on the actual confluence host after the URL mapping and this URI is invalid for
using it on the front-side of the mapping i.e. before mapping URLs. This leads
to the Webseal's error message shown above.

Suggested solution
^^^^^^^^^^^^^^^^^^
Instead of using the HttpServletRequest's method "getRequestURI()" for
determining the baseUrl automatically from the incoming request, confluence
should simply use the configured "Server Base Url" in method
AbstractHtmlGeneratingMacro. buildBaseUrl(...).

Workaround
^^^^^^^^^^
Unfortunatly I didn't find any in confluence
It seems that I'll have to change my public URL so that its path components match those of the non-public URL.