Finder Search in Mountain Lion -- broken?

Question

Since upgrading to Mountain Lion yesterday, my Finder Search does not operate the way it used to and I'm not getting the right results anymore.  I have already forced Spotlight to reindex by adding the entire drive and a disk image file to Privacy, and then removing them from Privacy.  Reindexing took about 45 minutes, but now it says it is done reindexing.  I have these same two issues both before and after the reindex.
If I have Finder displaying the files in the disk image and type a few letters for a filename (e.g., name matches great) in the search box, Finder Search cannot find the files in the disk image even though I can plainly see they are there.
I have Finder pointing to the entire main drive.  I search for name matches quiz.  I get 10 results, including 3 in the RE Class folder, plus seven others.  But, if I point Finder to the RE Class folder on the main drive, and do the same search, it shows me those three files (as it should), and if I click the button above the search results for "This Mac" to expand the search, it displays only those same three in the RE Class folder, and "Searching This Mac..." appears with a spinner at the bottom of Finder ... forever? About 20 minutes so far... (This used to be instantaneous.)  It cannot find all the other matching files it previously showed me are in multiple locations on the main drive.
Can someone tell me how to fix this?  Thank you.

Answer 1

Based upon my test results below, Apple Support has escalated this to the engineers for resolution.  It appears that the presence of any mounted DMG file is what precipitates the problem, and the problem goes away if I close the DMG, but I can't really search in my DMG files until this gets fixed.
<quoting my test results:>
I have done more testing this morning.
I had always worked with the Finder Preference > Advanced > When performing a search = Search the Current Folder.  I changed this back to Search This Mac before conducting the following tests.
My conclusion is that the presence of any open DMG is causing the problem.  Other connected drives (external) don't have any bearing; they work fine.
Test 1, with no DMG open:
Pointing to the David home folder.
Search Name=Dad
          This Mac=58
          Davidn=23
          This Mac=58
          David=23
This is as expected.  The counts include files from an external hard drive, together with the internal drive.
Test 2, with a DMG (Personal) open:
Pointing to the David home folder. 
Search Name=Dad
          This Mac=45  (Note that this number is lower than in test 1, and it should be higher by 3 because of the files in the DMG.  Expected count was 61.)
          David=23
          This Mac = <spinner>  (Expected 61)
          <cancel>
Test 3, with the DMG still open:
Search Name=Dad
          This Mac = 0  (Expected 61)
          David = 23
          This Mac = <spinner>  (Expected 61)
          <cancel>
At this point, I closed the DMG.
Test 4, with no DMG open:
Search Name=Dad          This Mac=58
          David=23
          This Mac=58
          David=23
This is as expected.  The counts include files from an external hard drive, together with the internal drive.
In addition, the tests I conducted yesterday, where I was directly searching in the DMG, remain the same: The first time the result is correct, and after that I only get beach balls.
Note that the DMG used for this test (Personal) is only 1 MB in size, and contains only 12 items in the root -- not a lot of searching to do.  I have tried to force Spotlight to reindex this file by moving it into and out of Privacy.  I never notice Spotlight do anything about that, but maybe it is too small to be noticeable.