As Jay says, it's to do with the extended character set not being read by archaic PM.
Try using Alt+0128 (Windows) to insert €
See this page in the PM Support KB: Unable to insert the Euro character in a publication
If you still have problems, download Adobe's free Type1 Euro fonts from here which will definitely solve it.
Iechyd da! John
I was going to mention that euro font, but I couldn't remember where I got it from.