Emacs 23 is running on a remote Linux box. It displays its frame on this local Windows box, using Cygwin’s X server. I used to be able to copy-paste any text from Emacs to any Windows application. Since after I upgraded from release 22 to 23, combining diacritics don’t come through any more.
Non-combined characters pass unharmed. For example, é (U+00E9, LATIN SMALL LETTER E WITH ACUTE) passes, whereas the (U+0065, U+0301) combination (LATIN SMALL LETTER E, COMBINING ACUTE ACCENT) does not: it comes out as e+Z
Such sequences still pass fine from Emacs to other X applications. They still pass fine from Emacs to X applications running on different boxes. They still pass fine from Emacs to local X applications. But when they get to cross the line between X and Windows, it stops working.
The only change that happened to the chain in months is that Emacs upgrade. The rest is untouched.
In case it’s of any help, XWin is lauched with the following command line:
exec XWin -clipboard -nowinkill -nounixkill -lesspointer -multiwindow
JB, this sounds like a bug on the Emacs end of things — though of course it could, from some other user’s point of view, be an “improvement” that makes Unicode work even better when used from some other server. See whether you can get any help or information by reporting a bug, and report back to us with a link so that we can keep up with it. And: good luck!