I have seen this error message occur when the version of the module that you're trying to install does not match the version of Perl (you can get more information about a particular search result using ppm's "describe" command). In the example below I try to install a ppm for MoreUtils that was built for 5.8 onto Perl 5.6.

C:\>perl -v

This is perl, v5.6.1 built for MSWin32-x86-multi-thread
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extraneous output deleted

ppm> desc 3
====================
Package 3:
    Name: List-MoreUtils
 Version: 0.16
  Author: Tassilo von Parseval <tassilo.von.parseval@rwth-aachen.de>
   Title: List-MoreUtils
Abstract: Provide the stuff missing in List::Util
Location: Kobes
Available Platforms:
       1. MSWin32-x86-multi-thread-5.8
====================
ppm> i 3
Package 3:
Error: no suitable installation target found for package List-MoreUtil
+s.
ppm>
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I chose a different module from the results list and MoreUtils installed just fine.