purely from your description i am not 100% sure what you mean. this might be due to your English (i suppose you are not a native speaker), but i think it would at least help if you’d provide an example .xrns so people can see what is happening for themselves. you could also try to do some screenshots or describe in more detail the actions you take.
well, i don’t seem to be able to get Renoise 2.7.2 to run on Linux. this is probably my own fault, but it means i cannot confirm what you are seeing. maybe i’ll be on Windows later and try it out there.
you should really upgrade your Linux distro indeed: Renoise has been tested only with newer distros because the Linux version is relatively new. your issue looks like one of the problems which Renoise had in the past with older versions of Compiz.
in case you hate the direction Ubuntu is taking since the last version (I do), you could take in consideration a migration to Linux Mint, which is Ubuntu compatible so you can retain your /home partition