Comment 27 for bug 542660

Benno - It's probably worth asking or searching the question in that forum (http://ubuntuforums.org/forumdisplay.php?f=328). 'Has anyone installed Lucid 10.04 on a i5,i7 iMac 11,1 or 27" '.

Gismo also indicated his workaround in #12 up above.

As to the specific postings where this was discussed try these:

http://ubuntuforums.org/showthread.php?t=1476226 <-- shows a workaround
http://ubuntuforums.org/showthread.php?t=1470389 <-- shows the original problem

I really dunno how much more I can add other than, it appears this problem still occurs. For now there are workarounds, try them out and then stumble into the next issue :)