Comment 4 for bug 771246

That's very interesting. When I run xmodmap from the console (w/o letting Gnome run it for me), I get no errors. Note that I've been using this xmodmap file since at least Maverick without problem. To answer the last question, yes the problem occurs in all applications. I did verify with xev the correct keycodes (that's always kind of a PITA).

Now here's where things get weird.

If I remove the Alt_R and Meta_R, I get errors from xmodmap (actually from the X server), but leaving the file as is works just fine.

Even more interesting: if I do not let Gnome run it on login, but instead run it from the terminal after login, the Alt key works better, but not perfectly. Holding (the new) Alt invokes the application menu, but hitting say Alt-<letter> in terminal does not pull down any menu. This does not seem to be a system-wide problem though, as Alt-<letter> appears to work fine in Computer Janitor or Mahjongg for example. So maybe *that's* just a bug in Terminal. (I've noticed that other keyboard shortcuts aren't working in Terminal either).

But back to Unity. There's clearly a difference between letting Gnome run my xmodmaprc and running it manually after login. I can use that as a workaround for now. I'll be bringing this machine to UDS-O so if you're going to be there, perhaps we can take a look together.

Cheers.