I now have a full solution for my remote problems. I bought an IR keyboard from ebay (http://tinyurl.com/6mf2fwm). After programming all necessary keys and adding xbmc as an activity, I can now fully control Linhes/Myth and XBMC.
Compared to the hair loss of trying to solve the remote issues under 7.2, the keyboard solution was easy. Please note that I changed the Linhes setup to no remote and default receiver. The only outstanding issue is that for some reason the remote receiver is not always detected on a reboot, but works fine from a cold start, i.e. shutdown and then startup. I am still looking into that minor issue.