sorry i had to nip out hence the short post.
Select your emule location when prompted to, this is where you have the known.met (which stores the hashes and file details) and select your temp directory.
Then click the top right button, select the part file in question. It will compare against your known.met and then generate a new part.met.
Now start up emule and it will rehash
The circuit was reset about 4 hrs before i posted my first response and one file was corrupt. Carrying out the above mended it and it's downloading again
Renaming is *not* a good idea, you will have an incomplete or corrupt file. Sometimes it plays fine, but it will have errors that aren't in the proper file and it will have a different hash.