http://bugs.winehq.org/show_bug.cgi?id=15203
--- Comment #2 from Dmitry Timoshkov dmitry@codeweavers.com 2008-09-10 02:15:20 --- (In reply to comment #0)
Created an attachment (id=15960)
--> (http://bugs.winehq.org/attachment.cgi?id=15960) [details]
assigns ISO_Level3_Shift as VK_RMENU in X11DRV_InitKeyboard On Ubuntu 8.04, the right alt key generates ISO_Level3_Shift (keysym == 0xfe03), which wine doesn't currently recognize as the right alt button.
This sounds like a bug in Ubuntu keyboard layout. Right alt should generate XK_Alt_R (0xffea) keysym. Have you tried to report this to Ubuntu devs?