giancarlo,
The problem is that the change you're making only differs in capitalization. You're searching for "stmoritz" and changing it to "StMoritz". The find and replace in file names is not very sophisticated and since most filesystems are case-preserving but case-insensitive, "stmoritz" and "StMoritz" are the same file name. So the rename fails.
I'll make the renaming more sophisticated (rename to a temporary name and then rename to the final name) but in the meantime, you can do two find and replace operations. The first one search for "stmoritz" and replace with "temp", and for the second find and replace search for "temp" and replace with "StMoritz". That should work fine.
-Kirk
