If you used ACE Photo Contrast Enhancement (produces high contrast images like some of the commercial packages) you may have noticed updating to the latest version of gimp breaks it.

Here is the solution:
It complains about
libintl-8.dll missing

So, I set out to find this dll - knowing it was an opensource package, it had to be out there somewhere.

Go to this site:
http://rpm.pbone.net/
Go to search and put in the name of the DLL above. It will return a list of RPM packages with the DLL in it.
Download a package.

You won't be able to open it natively on a windows machine. You need a windows program called 7zip. It is freeware - google for it - install it. Go to the programs options and set it as the default for .rpm files

Double click on the file and extract it - and look for the DLL above.

Copy and paste it to where you installed the ACE plugin

C:\Documents and Settings\username\.gimp-2.6\plug-ins

Now when you start gimp - it will complain about the libiconv-2.dll missing. Rinse lather and repeat for this dll and do the same thing as above, only now search for this name.

Download the RPM
Extract libiconv-2.dll (the file you need)
Place it in the same folder as above.

If all goes well you can start using your ACE plugin again. It worked for me - YMMV. . .